Open Access
Volume 10, 2024
Article Number 10
Number of page(s) 7
Section Knee
Published online 28 February 2024

© The Authors, published by EDP Sciences, 2024

Licence Creative CommonsThis is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


For the treatment of medial femorotibial osteoarthritis (OA) in conjunction with anterior knee laxity, several surgical treatments are available [1]. Unicompartmental knee replacement (UKR) is generally not recommended in the presence of concomitant anterior cruciate ligament (ACL) deficiency, and traditionally, total knee replacement (TKR) has been safely done in this setting [2]. However, considering these surgical options, UKR has advantages over TKR, including less invasiveness, lower blood loss, bone stock preservation, a quicker recovery, and improved joint kinematics [35].

For these reasons, more recently, ACL-deficient patients with isolated medial OA demonstrated to benefit from fixed-bearing UKR implanted with a lower grade of tibial slope in order to compensate for anterior tibial translation [6]. However, to overcome the potential risks of posterior femoral shift brought by ACL insufficiency and increased incidence of aseptic loosening, a surgical strategy allowing concomitant UKR and ACL reconstruction has been successfully proposed (Table 1) [719].

Table 1

Summary of all available studies on combined UKR and ACL reconstruction.

Satisfactory mid-term results of this surgical procedure have been reported, although this is a technically demanding procedure which may carry drawbacks such as impingement with the neoligament and improper sizing of the prosthetic tibia, and the relatively high rate of complications reported in some studies may limit this surgical option to become mainstream [19, 20].

This study compares the subjective, radiological, and functional results of combined medial UKR with ACL reconstruction vs. TKR. The hypothesis was that the combined treatment may offer comparable or superior outcomes without adding postoperative complications.

Patients and methods

Study design

Fourteen consecutive cases suffering from medial OA and ACL deficiency were treated from 2006 to 2010 with combined UKR and ACL reconstruction. Twelve of them (86%) were successfully monitored up to 10 years after surgery. Prospectively collected clinical outcomes were retrieved from the senior’s author database and retrospectively analyzed. Patients were matched 1:2 to a control group of 24 patients who received TKR for primary idiopathic OA over a period of 2 years (2009–2011) having the same average follow-up (10.0 years). Regarding age, the male-to-female ratio, and body mass index (BMI), the two groups were comparable. BMI > 30, OA involving other compartment than medial, varus knee deformity and/or tibial slope >10°, presence of patellofemoral-related problems were exclusion criteria for UKR. Every time OA was expanded to many compartments, TKR was carried out.

In group A, the mean age at surgery was 54 years (SD: 3.9), while in group B, it was 55.8 years (SD: 4.2) (Table 2). A single surgeon carried out each procedure. Written informed consent was obtained. The study was carried out in accordance with the recommendations made by the Institution’s Ethical Committee and conducted according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. Data regarding clinical and radiological assessment up to 10 years after surgery were retrieved from the senior’s author database. The most recent follow-up was considered. Ethical approval was not required for the follow-up of this observational analytic study with a retrospective design on well-established surgical procedures, as the patients’ reported outcomes used are part of routine follow-up at the authors’ institution.

Table 2

Patient demographics and anthropometric data.

Surgical procedure and rehabilitation protocol

In the case of UKR combined with ACL reconstruction, surgery was performed as previously described [9] using Allegretto unicondylar fixed-bearing prosthesis (Zimmer-Biomet Orthopedics, Warsaw, IN, USA) and autologous hamstring tendon grafts fixed proximally with either a RIGID-FIX equipment (DePuy Mitek, Raynham, MA, USA) or a Retrobutton device (Arthrex, Naples, FL). The distal fixation was achieved through a BioRCI screw (Bioabsorbable Rounded Cannulated Interference, Smith & Nephew Inc. Andover, MA, USA).

All patients in group B underwent medial parapatellar arthrotomy for implantation of a cemented posterior stabilized Vanguard Complete Knee System (Zimmer-Biomet Orthopedics) without patellar resurfacing. The day following surgery, a brace-free post-operative rehabilitation plan was initiated. It included joint motion exercises, an immediate return to full knee extension, and progressive weight-bearing ambulation with crutches. Walking with some weight bearing was permitted for the first four weeks while using two crutches.

Follow-up assessment

The assessment included the Knee Osteoarthritis Outcome score (KOOS), Oxford Knee score (OKS), and Western Ontario and McMaster (WOMAC) index of OA. A radiological assessment was conducted with standard radiographs in order to get information about any presence of loosening of the components. Radiolucencies were judged as physiological or pathological according to criteria expressed by Goodfellow et al. [21].

Statistical analysis

SPSS Statistics for Windows®, Version 21.0 (IBM Corp., Armonk, NY) was used to analyze the data that had been extracted. The pre-operative and follow-up status, as well as any differences between the two groups, were compared using the Wilcoxon signed-rank test. Differences were deemed statistically significant with p-value < 0.05.


Overall, no major complications (fractures, infections, thromboembolism) were reported.

Superficial wound dehiscence occurred in two patients in group B, while stiffness was reported in three patients following TKR. One female patient in group A got a revision TKR with symptom relief three years after surgery because of pain persistence and OA development in the lateral compartment.

Post-operatively, there was a statistically significant change, as evidenced by increases in the mean overall KOOS score, OKS, and WOMAC index (p < 0.001, Table 3).

Table 3

Comparison between pre-operative and follow-up status.

Group B scored lower on the baseline questionnaires, although the difference was not statistically significant. At the latest follow-up, there was no significant difference between the groups concerning KOOS, OKS, or WOMAC scores (p = n.s., Table 4).

Table 4

Comparison between groups at final follow-up.

Radiographic follow-up was performed up to 10 years after surgery, although for some patients most updated X-rays were taken at 5 years post-operatively. Thus, for group A, the average radiographic follow-up was 7.9 years (SD: 2.6), while for group B it reached 8.8 years (SD: 2.2). At the most recent follow-up, there were no radiographic indications of implant loosening or pathologic radiolucent lines.


The most significant conclusion of the current study is that UKR combined with ACL reconstruction offers clinical and radiographic results comparable to TKR 10 years following surgery with no increased risk of complications. In the medium-long term, both therapies enhance postoperative clinical and functional results. At the follow-up, there were no statistically significant differences between the two groups in terms of functional results.

Foissey et al. reported on 10 patients after robotic-assisted UKR combined to hamstring ACL reconstruction after an average follow-up of 45 months. The mean post-operative International Knee postoperative function score was 93, mean Tegner score was 4.5 [10]. Two patients underwent arthroscopic arthrolysis following postoperative arthrofibrosis. In the study by Tian et al. on 28 patients treated by combined UKR and ACL reconstruction, 4 years after surgery, the average OKS was 43, and Tegner activity level reached the mean value of 5.3 [7].

Jaber et al. followed up for 10 years 23 patients who had undergone mobile-bearing UKR combined with ACL reconstruction [12]. The average Lysholm score was 85.5, while the mean OKS was 40. None of the patients reported knee instability and all of them returned to sporting and physical activities. The authors reported a survival rate of 91.4% at 14.5 years. Similarly to our case series, one patient received a conversion procedure one year after surgery due to the progression of symptomatic lateral knee OA.

In the study by Kurien et al., 24 patients underwent simultaneous ACL reconstruction and medial UKR. After an average follow-up of 5.1 years, the mean OKS score was 46, while the average Lysholm score was 92. Consistently to our study, fixed-bearing UKR was chosen to avoid the risks of bearing dislocation [11].

According to our results, 10 years after surgery, there was no discernible difference between the two groups regarding KOOS, OKS or WOMAC scores, showing that combined UKR and ACL reconstruction allow comparable outcomes to TKR. This suggests that this combined procedure is effective when approaching relatively young and active individuals with ACL insufficiency and advanced unicompartmental knee OA. Additionally, the advantages of this combined approach over TKR are less invasiveness and blood loss, and better knee kinematics.

Nowadays, patients suffering from knee OA are more likely to be willing to return to physical activity and active daily living [22]. Advancements in surgical methods and prosthetic designs may enable patients to return to pre-operative levels of physical activity [23].

Drawbacks of this combined procedure include the fact that it is technically challenging, and carries potential risks of post-operative arthrofibrosis, ACL graft impingement, and tibial base plate under-sizing. To reduce these disadvantages, simultaneous ACL reconstruction and UKR should be preferable compared to a staged one. In fact, as suggested by Pandit et al., a more vertical drilling and lateral exit of the tibial tunnel aperture can prevent graft impingement of the neo-ligament [13]. Another potential issue related to this surgical approach is the longer post-operative rehabilitation period compared to TKR. To overcome this drawback, compliance from the patient is essential for a successful outcome. According to Derreveaux et al., in physically active patients with unicompartmental knee OA, combining UKR with additional surgery to manage relative contraindications to TKR is an effective strategy that yields satisfactory results at short-term follow-up. According to the authors, it should only be used on patients who have received comprehensive counseling about all available therapeutic alternatives and for whom TKR is likely to yield disappointing outcomes [24].

Eventually, concerning patients’ selection, only patients with OA secondary to ACL deficiency should be eligible for this combined procedure. In fact, for patients whose main problem is cartilage deterioration and secondary ACL instability, TKR should be preferred due to the presence of contracture to the medial collateral ligament and wear on the other compartments [12, 20].

The present study has some limitations, including its retrospective character and the limited study population, due to the highly selective patient selection criteria required for this operation. The small sample size may not have allowed for the detection of small differences between groups. Postoperative results showed a tendency in favour of ACL reconstruction combined with UKR, although not statistically significant. Further multi-center studies with larger cohorts are warranted to find more reliable results and conclusions.


UKR combined with ACL reconstruction is a valid therapeutic option for young and active patients with a primary ACL injury who develop secondary OA and confirms subjective and objective clinical improvement up to 10 years after surgery.


The Study was supported by the Italian Ministry of Health – Ricerca Corrente.

Conflicts of Interest

The authors declare that they have no relevant financial or non-financial interests to report.

Data availability statement

Data are available on request from the authors.

Author contribution statement

Conceptualization, C.L., A.V.; methodology, C.L., C.T.; software, E.B., V.M.; formal analysis, C.L., C.T.; data curation, E.B., V.M.; writing – original draft preparation, C.L.; writing – review and editing, A.V.; supervision, A.V.

Ethics approval

Ethical approval was not required for the follow-up of this observational analytic study with a retrospective design on well-established surgical procedures, as the patient-reported outcomes used are part of routine follow-up at the authors’ Institution.

Informed consent

All patients gave informed consent.


  1. Schneider A, Gaillard R, Gunst S, Batailler C, Neyret P, Lustig S, Servien E (2020) Combined ACL reconstruction and opening wedge high tibial osteotomy at 10-year follow-up: excellent laxity control but uncertain return to high level sport. Knee Surg Sports Traumatol Arthrosc 28 (3), 960–968. [CrossRef] [PubMed] [Google Scholar]
  2. Williams RJ III, Wickiewicz TL, Warren RF (2000) Management of unicompartmental arthritis in the anterior cruciate ligament deficient knee. Am J Sports Med 28, 749–760. [CrossRef] [PubMed] [Google Scholar]
  3. Brilliant ZR, Garvey MD, Haffner R, Chiu YF, Mayman DJ, Blevins JL (2023) Unicompartmental knee arthroplasty patients have lower joint awareness and higher function at 5 years compared to total knee arthroplasties: a matched comparison. J Arthroplasty 38 (8), 1464–1469. [CrossRef] [PubMed] [Google Scholar]
  4. O'Neill CN, Gowd AK, Waterman BR, Kates SL, Patel NK (2022) Significant reduction in short-term complications following unicompartmental versus total knee arthroplasty: a propensity score matched analysis. J Arthroplasty 37 (10), 2014–2019. [CrossRef] [PubMed] [Google Scholar]
  5. Annapareddy A, Mulpur P, Prakash M, Suhas Masilamani AB, Eachempati KK, Gurava Reddy AV (2023) Partial versus total knee arthroplasty for isolated antero-medial osteoarthritis – an analysis of PROMs and satisfaction. SICOT J 9, 11. [CrossRef] [EDP Sciences] [PubMed] [Google Scholar]
  6. Zumbrunn T, Schütz P, von Knoch F, Preiss S, List R, Ferguson SJ (2020) Medial unicompartmental knee arthroplasty in ACL-deficient knees is a viable treatment option: in vivo kinematic evaluation using a moving fluoroscope. Knee Surg Sports Traumatol Arthrosc 28 (6), 1765–1773. [CrossRef] [PubMed] [Google Scholar]
  7. Tian S, Wang B, Wang Y, Ha C, Liu L, Sun K (2016) Combined unicompartmental knee arthroplasty and anterior cruciate ligament reconstruction in knees with osteoarthritis and deficient anterior cruciate ligament. BMC Musculoskelet Disord 17, 327. [CrossRef] [PubMed] [Google Scholar]
  8. Tecame A, Savica R, Rosa MA, Adravanti P (2019) Anterior cruciate ligament reconstruction in association with medial unicompartmental knee replacement: a retrospective study comparing clinical and radiological outcomes of two different implant design. Int Orthop 43 (12), 2731–2737. [CrossRef] [PubMed] [Google Scholar]
  9. Ventura A, Legnani C, Terzaghi C, Macchi V, Borgo E (2020) Unicompartmental knee replacement combined to anterior cruciate ligament reconstruction: midterm results. J Knee Surg 33 (11), 1152–1156. [CrossRef] [PubMed] [Google Scholar]
  10. Foissey C, Batailler C, Shatrov J, Servien E, Lustig S (2023) Is combined robotically assisted unicompartmental knee arthroplasty and anterior cruciate ligament reconstruction a good solution for the young arthritic knee? Int Orthop 47 (4), 963–971. [CrossRef] [PubMed] [Google Scholar]
  11. Kurien T, Stragier B, Senevirathna S, Geutjens G (2022) Excellent outcomes with combined single stage Physica ZUK medial unicompartment knee replacement and anterior cruciate ligament reconstruction results in young, active patients with instability and osteoarthritis with a mean follow up of 5 years. Knee 36, 114–119. [CrossRef] [PubMed] [Google Scholar]
  12. Jaber A, Kim CM, Barié A, Streit M, Schmitt H, Clarius M, Merle C, Bangert Y (2023) Combined treatment with medial unicompartmental knee arthroplasty and anterior cruciate ligament reconstruction is effective on long-term follow-up. Knee Surg Sports Traumatol Arthrosc 31 (4), 1382–1387. [CrossRef] [PubMed] [Google Scholar]
  13. Pandit H, Beard DJ, Jenkins C, Kimstra Y, Thomas NP, Dodd CA, Murray DW (2006) Combined anterior cruciate ligament reconstruction and Oxford unicompartmental knee arthroplasty. J Bone Joint Surg Br 88, 887–892. [CrossRef] [Google Scholar]
  14. Dervin GF, Conway AF, Thurston P (2007) Combined anterior cruciate ligament reconstruction and unicompartmental knee arthroplasty: surgical technique. Orthopedics 30, 39–42. [PubMed] [Google Scholar]
  15. Krishnan SRSR, Randle R (2009) ACL reconstruction with unicondylar replacement in knee with functional instability and osteoarthritis. J Orthop Surg Res 4, 43. [CrossRef] [PubMed] [Google Scholar]
  16. Tinius M, Hepp P, Becker R (2012) Combined unicompartmental knee arthroplasty and anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc 20, 81–87. [CrossRef] [PubMed] [Google Scholar]
  17. Weston-Simons JS, Pandit H, Jenkins C, Jackson WF, Price AJ, Gill HS, Dodd CA, Murray DW (2012) Outcome of combined unicompartmental knee replacement and combined or sequential anterior cruciate ligament reconstruction: a study of 52 cases with mean followup of five years. J Bone Joint Surg Br 94, 1216–1220. [CrossRef] [Google Scholar]
  18. Kennedy JA, Molloy J, Mohammad HR, Mellon SJ, Dodd CA, Murray DW (2019) Mid- to long-term function and implant survival of ACL reconstruction and medial Oxford UKR. Knee 26, 897–904. [CrossRef] [PubMed] [Google Scholar]
  19. Iriberri I, Suau S, Payán L, Aragón JF (2019) Long-term deterioration after one-stage unicompartmental knee arthroplasty and anterior cruciate ligament reconstruction. Musculoskelet Surg 103 (3), 251–256. [CrossRef] [PubMed] [Google Scholar]
  20. Legnani C, Muzzi S, Peretti GM, Borgo E, Ventura A (2021) Anterior cruciate ligament reconstruction combined to partial knee replacement in active patients with ACL deficiency and knee osteoarthritis. Phys Sportsmed 49 (1), 12–17. [CrossRef] [PubMed] [Google Scholar]
  21. Goodfellow J, O’Connor J, Dodd C, Murray D (2006) Unicompartmental arthroplasty with the Oxford knee, 1st edn. Oxford: Oxford University Press. [Google Scholar]
  22. Ventura A, Macchi V, Borgo E, Legnani C (2022) Shift to low-impact sports and recreational activities following total knee replacement. Int J Artif Org 45, 952–956. [CrossRef] [PubMed] [Google Scholar]
  23. Legnani C, Macchi V, Peretti GM, Coccioli G, Borgo E, Ventura A (2023) Return to sports and physical activities following mobile-bearing unicompartmental knee replacement. J Biol Regul Homeost Agents 37 (12), 6545–6549. [Google Scholar]
  24. Derreveaux V, Schmidt A, Shatrov J, Sappey-Marinier E, Batailler C, Servien E, Lustig S (2022) Combined procedures with unicompartmental knee arthroplasty: high risk of stiffness but promising concept in selected indications. SICOT J 8, 4. [CrossRef] [EDP Sciences] [PubMed] [Google Scholar]

Cite this article as: Legnani C, Borgo E, Macchi V, Terzaghi C & Ventura A (2024) Unicompartmental knee replacement combined with anterior cruciate ligament reconstruction provides comparable results to total knee replacement with no increased risk of complications. SICOT-J 10, 10

All Tables

Table 1

Summary of all available studies on combined UKR and ACL reconstruction.

Table 2

Patient demographics and anthropometric data.

Table 3

Comparison between pre-operative and follow-up status.

Table 4

Comparison between groups at final follow-up.

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