Skip to main content
  • Original Paper
  • Open access
  • Published:

Satisfactory outcomes of patellar tendon reconstruction using achilles’ tendon allograft with bone block after infected total knee arthroplasty



Extensor mechanism disruption is an uncommon and devastating complication after total knee arthroplasty. It negatively affects patients’ quality of life and leads to significant functional limitations and the inability to stand and walk. The purpose of the present study was to evaluate the outcomes of the extensor mechanism reconstruction using Achilles’ tendon allograft after infected total knee arthroplasty. It was hypothesized that it is a safe procedure and that patients will present good clinical and functional results.


Ten patients treated for infra-patellar extensor mechanism disruption after infected total knee arthroplasty were prospectively followed for two years. The mean age of patients was 70.8 (range 55–85), with a median BMI of 28.72 ± 2.2 kg/m2. All patients underwent reconstruction using a fresh frozen Achilles tendon allograft. Preoperative and postoperative evaluation included knee-related clinical and functional assessment based on objective and subjective scores, including the knee flexion, the extension lag, the Knee Society Score (KSS) clinical and functional, and the visual analog scale (VAS) for pain at 12 and 24 months. Radiological evaluation was also performed using the Caton-Deschamps index. Reported complications were also recorded.


Clinical and functional outcomes recorded significant improvements (p < 0.05) at the final follow-up compared with baseline as follows: Knee flexion was improved from 66° ± 4.8 to 99.7° ± 3.9, and the extension lag was decreased from 28.3° ± 4.4 to 9° ± 2.7. The mean KSS clinical and functional were also improved from 22.6 ± 7.9 to 73.4 ± 3.9 and from 10 ± 13.8 to 55 ± 13.8, respectively. The VAS for pain was decreased from 8.1 ± 1.2 to 1.9 ± 1.2. The Caton-Deschamps index demonstrated a tendency to patella Alta. Two treatment failures were recorded, one patellar dislocation and one re-rupture revised to arthrodesis.


Extensor mechanism reconstruction using Achilles’ tendon allograft after infected total knee arthroplasty is an efficient and safe procedure for infra-patellar disruption. The present study’s findings demonstrate that most of the patients (80%) presented significant clinical and functional improvement at two-year follow-up.


Patients presenting extensor mechanism (ΕΜ) disruption due to infection after total knee arthroplasty (TKA) require a highly challenging injury treatment [2]. The majority of them have numerous previous surgical procedures which negatively affect the soft tissue quality and lead to significant functional limitations and inability to stand and walk [16].

Indeed, extensor mechanism disruption is a severe and challenging complication following total knee arthroplasty leading to chronic pain, limited range of motion, extension lag, and gait abnormalities [13] and most often occurs as a patellar tendon rupture [9]. The reported incidence is between 0.1% and 2.5%, and the commonly suggested predisposing factors include multiple prior operations, stiffness, patella baja, obesity, systemic pathologies or medications, and infections [18].

Multiple treatment modalities are available to cope with these significant complications, including two-stage revision arthroplasty combined with extensor mechanism reconstruction, knee arthrodesis, or amputation above the knee [15, 17]. However, there is still no clear consensus on treating these patients, and limited data exist in the literature to evaluate their functional outcomes [24].

Either pre-or post-arthroplasty infection is another devastating complication that harms patients' quality of life and autonomy and leads to soft tissue degeneration and, in time, extensor mechanism disruption necessitating revision surgery [22]. The admixture of these complications is rare, making treatment even more challenging for both the patient and the surgeon.

Surgical reconstruction of the extensor mechanism, remains challenging and is considered a salvage procedure to avoid the functional limitation of arthrodesis or amputation and maintain a greater level of knee function. This technique mainly includes synthetic material or allografts, presenting acceptable results [11]. Most often utilized allografts are either the whole extensor mechanism comprising quadriceps tendon, patella, patellar tendon, tibial tubercule block, or the Achilles’ tendon with calcaneum bone block [5, 23].

However, to our best knowledge, no clinical study examined reconstruction with Achilles’ tendon allograft in the case of previously infected total knee arthroplasty. The purpose of the present study was to evaluate the outcomes of extensor mechanism reconstruction for infrapatellar disruption using Achilles’ tendon allograft after infected total knee arthroplasty. It was hypothesized that this procedure could provide good clinical and functional outcomes.

Materials and methods

The study included ten patients treated for infra-patellar extensor mechanism rupture using Achilles’ tendon allograft after infected total knee arthroplasty between 2015 and 2019. The diagnosis of infected total knee arthroplasty was made according to the International Consensus on Periprosthetic Joint Infection criteria [19] or its later modification [20].

All patients reported an inability to walk and to do straight leg raise. The extensor mechanism rupture was diagnosed either clinically and confirmed echographically or intraoperatively during the prior surgical procedures. It is noted that the insufficiency of the extensor mechanism was identified after the initial diagnosis of infection as part of the infection process. The patients had multiple previous surgeries as shown in Table 2, and the salvage procedure consisting in the revision of the total knee arthroplasty combined with the extensor mechanism allograft reconstruction was performed at least three months after infection eradication.

After the diagnosis of the infection, the first step of the treatment was the removal of the initial components and cement, extensive debridement of the joint cavity, and implantation of an antibiotic-impregnated (Gentamycin) articulating spacer.

The complete inclusion and exclusion criteria are listed in Table 1. Analytical demographic characteristics of the study population are provided in Table 2.

Table 1 Inclusion and exclusion criteria of eligibility
Table 2 Patient’s demographic characteristics

Surgical technique

Classical revision total knee arthroplasty principles were followed for proper prosthesis implantation using rotating modular hinge design implants. Extensor mechanism reconstruction was performed at the same surgical time as the revision implantation. A 24–26 cm long fresh-frozen Achilles’ tendon allograft with bone attachment to the calcaneum was used (Fig. 1a, b). One of the previous incisions was used to expose the whole extensor apparatus extensively. A medial parapatellar arthrotomy was performed. After the final placement of the components, a rectangular anterior tibial bone “window” of approximately 3 cm long by 2 cm wide and 1,5 cm deep was performed just inferior to the patellar tendon insertion at the anterior tibial tubercle. The calcaneal bone block was prepared to fit in the “window.” It was softly impacted into the tibial defect, and then it was fixed with 4.0 mm screws and metallic cerclages. The screw direction was angled to avoid the tibial stem. The patella was centered in the trochlea and verified in full extension and 30 degrees of flexion to achieve the optimal height. A split to the patellar tendon was performed (Fig. 1c), and the Achilles’ tendon was sutured with a number 2 nonabsorbable sutures in full extension to the underlying extensor mechanism (Fig. 1 d, e). Subcutaneous tissue and skin closure were completed, and a compressive dressing was applied. Radiological evaluation was performed (Fig. 1.f).

Fig. 1
figure 1

Different steps of extensor mechanism reconstruction. a: Achilles’ tendon allograft, b: graft preparation, c: patellar tendon split, d: the Achilles’ tendon was sutured with a number 2 nonabsorbable sutures in full extension, e: final placement of the graft, f: Radiographic evaluation

Postoperative protocol

After surgery, all patients were placed in an extension brace for four weeks and allowed weight bearing as tolerated. No active straight leg raises, or quad sets were permitted during this period. A functional brace was placed from the 5th week, allowing an active flexion up to 30° initially and then gradually increased each week for 15°. At two months, post-operative patients were allowed a range of motion up to 90° with full weight-bearing. Straight leg raises exercises were also allowed. The brace was removed three months after surgery, and the range of motion was unrestricted.

Evaluation of outcomes

All patients were clinically evaluated at 12 and 24 months. Primary outcomes were the knee flexion and the extension lag measured with a manual goniometer with the patient in the supine position from the lateral side of the knee. Secondary outcomes included the Knee Society Score (KSS) clinical and functional, the visual analog scale (VAS) for pain. Clinical failure was defined as an extension lag higher than 20° or cases needing revision surgery. Complications were recorded as well. Standard radiological evaluation including anteroposterior, lateral and patellar views was performed in all the follow-up intervals. The patellar height was also calculated using the Caton-Deschamps index. All patients agreed to follow the same rehabilitation protocol.

Statistical analysis

Statistical analysis was performed by an independent statistician using IBM SPSS Statistics (IBM Corp. Released 2020. IBM SPSS Statistics for Windows, Version 27.0. Armonk, NY: IBM Corp). One-way repeated measures ANOVA was applied to analyze outcomes between pre-operative and post-operative findings after checking normality assumptions using the Shapiro–Wilk test. If the condition of sphericity had not been met, the p-values were adjusted according to Greenhouse–Geisser correction. As the within-subjects ANOVA showed a significant difference, pairwise comparisons were used, applying Bonferroni corrections. The significance level was set at 5%.


All patients who met the eligibility criteria were included in this study and prospectively followed for at least 24 months. The mean follow-up was of 34 months (range 24–53 months). Complete data were recorded for all patients. The patients had many previous surgical procedures varied from 5 to 9. These procedures comprise partial meniscectomy, primary total arthroplasty, revision total knee arthroplasty, arthroscopic or open debridement, and spacer implantation. Statistically, significant improvement was found in all clinical and functional assessment tools (p < 0.05). More precisely, the knee flexion was increased, reaching a final value of approximately 100°, while the extension lag was decreased to less than 10°. KSS clinical and functional scores were 73.4 and 50, respectively, and VAS for pain was about 2 at the last follow-up. Detailed outcomes are provided in Table 3. Radiological evaluation revealed no sign of implant failure or periprosthetic fracture. Two treatment failures were recorded and thus, excluded from further analysis. One patient had a postoperative patellar dislocation (Fig. 2a) which negatively affected extensor mechanism function, and another one had a re-rupture of the extensor mechanism requiring a revision to arthrodesis (Fig. 2b). The remaining patients were satisfied as they could actively raise their legs and climb stairs without crutches. The mean Caton-Deschamps index was 1.5 and demonstrated a tendance to a patella alta (Fig. 2c).

Table 3 Summary of Outcomes
Fig. 2
figure 2

a. X-ray of patellar dislocation b. X-ray of knee arthrodesis c. Caton-Deschamps index


The most important finding of the present study was that extensor mechanism reconstruction following infected total knee arthroplasty with Achilles’ tendon allograft was shown to be an efficient and safe procedure in the majority of patients with good clinical results within two-year of follow-up. Nevertheless, 20% of the patient presented a treatment failure.

The overall outcome was satisfactory, with a significant improvement in knee flexion, extension lag, KSS clinical and functional scores and VAS for pain. Radiological evaluation revealed a tendance to patella alta according to the Caton-Deschamps index.

Previous studies reported surgical reconstruction outcomes using synthetic material or allografts after total knee arthroplasty [1, 6, 13, 14]. Achilles’ tendon allograft with calcaneal bone block has been widely used for disrupted patellar tendon reconstruction after aseptic TKA and presented the most successful results [10, 13, 21, 25].

For instance, Crossett et al. [10] studied nine patients with a mean follow-up of 28 months. They found that the average postoperative extensor lag had decreased from 44° to 3°, with six patients demonstrating no extensor lag, and the average range of motion had increased from 880 to 107°. Moreover, all patients reported improved ability to walk and climb stairs. They concluded that it could be a faithful reconstruction of a ruptured patellar tendon and may be particularly suited for patients in whom multiple prior operations compromised the extensor mechanism.

Additionally, Wise et al. [25] reported that Achilles’ tendon allograft is a reliable and durable treatment for patients presenting extensor mechanism disruption following TKA. They retrospectively evaluated seventeen cases of extensor mechanism failure following total knee arthroplasty in sixteen patients who underwent reconstruction using Achilles’ tendon allograft assessed at an average of 45.7 months. The ten cases involved patellar tendon disruption, and the study demonstrated an average postoperative extensor lag and flexion of 9.6° and 105.1°, respectively.

To date, limited data exist in allograft reconstruction after infected total knee arthroplasty. Indeed, no recent studies focus only on this demanding population. Even so, some authors include limited cases in previous case series [3, 12].

In fact, Lamberti et al. [12] compared mid-term results of three different reconstructive techniques for chronic patellar rupture. Patients underwent reconstruction either with extensor mechanism or Achilles’ tendon allograft or quadriceps tendon autograft with semitendinosus tendon augmentation. They included seven patients in each group, and they reported statistically significant changes in all groups for the mean knee society score (KSS) and the mean extension lag. However, patients treated with Achilles’ tendon allograft presented better improvement from 34.9 ± 21.3 to 87.7 ± 14.3 and from 54° ± 17.2° to 2° ± 1.5°, respectively. Thus, the authors consider this technique the gold standard for repairing a chronic patellar tendon lesion after total knee arthroplasty. Nevertheless, it should be noted that only two out of the seven patients in this group presented a previous periprosthetic infection.

Ares et al. [3] reported an observational study of five patients diagnosed with patellar tendon rupture after total knee replacement and surgically treated with Achilles’ tendon allograft reconstruction. However, only one patient had a prior infection. All patients presented a mean extensor lag of 1ο and flexion of 102°, and they were able to walk without crutches at a mean of 25 months postoperatively. The only complication recorded was one patellofemoral pain syndrome.

The present study evaluated ten patients treated with Achilles’ tendon allograft reconstruction for infrapatellar rupture after septic TKA. An improvement was observed both in clinical and functional outcomes. Moreover, KSS clinical and functional scores were improved, reaching at the final follow-up 73.4 and 50 points, respectively. Finally, the VAS score was decreased from 8 to 2. These outcomes indicate a notable change in the patient’s quality of life.

These findings are in accordance with previously reported data presenting the Achilles tendon allograft as an effective treatment for reconstructing ruptured patellar tendon [8, 10, 25]. Barrack et al. [4] reported a summary average of clinical and functional Knee Society Score, which improved from 32 to 128 points, representing a highly significant improvement. Crosset et al. [10], in their retrospective study, included nine patients treated for acute or chronic patellar tendon rupture after total or revision knee arthroplasty. They observed an improvement in KSS clinical and functional scores from 26 to 81 and from 14 to 53 points, respectively. This improvement is slightly superior to that in the present study. However, it should be noted that their study included only two cases with a prior deep infection, which partly could explain the results.

Two complications were recorded in the current study. It has been well documented that the initial allografts’ tensioning is crucial to avoiding persistent extension lag and clinical failure [7]. Therefore, all the allografts were sutured under high tension in full extension. However, a patellar dislocation due to sutures loosening was observed. Thus, very rigid fixation of the graft could be complicated with a suture loosening in patients presenting poor soft tissue quality due to numerous previous procedures. The second complication was a re-rupture of the extensor mechanism following low energy trauma and treated with knee arthrodesis.

There are also specific limitations that have to be considered in the current study. This study is a case series with a low number of participants and without a comparative group of other possible grafts and thus involved selection bias. Nevertheless, due to septic total knee arthroplasty, extensor mechanism disruption is a rare complication that makes difficult the inclusion of patients in this type of study. Hence, future studies with more patients and a longer follow-up are needed to validate these data. Another limitation is the absence of cost-effective and psychological aspects analysis. Moreover, the limited follow-up period after this procedure is recognized as another potential limitation.


Extensor mechanism reconstruction using Achilles' tendon allograft after infected total knee arthroplasty is an efficient and safe procedure for infrapatellar disruption. The present study's findings demonstrate that the majority of the patients presented significant clinical and functional improvement within two-year of follow-up. However, we recorded 20% of treatment failure.

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.


  1. Abdel MP, Salib CG, Mara KC, Pagnano MW, Perry KI, Hanssen AD (2018) Extensor Mechanism Reconstruction with Use of Marlex Mesh: A Series Study of 77 Total Knee Arthroplasties. J Bone Joint Surg Am 100:1309–1318

    Article  Google Scholar 

  2. Anderson LA, Culp BM, Della Valle CJ, Gililland JM, Meneghini RM, Browne JA et al (2018) High Failure Rates of Concomitant Periprosthetic Joint Infection and Extensor Mechanism Disruption. J Arthroplasty 33:1879–1883

    Article  Google Scholar 

  3. Ares O, Lozano LM, Medrano-Nájera C, Popescu D, Martínez-Pastor JC, Segur JM et al (2014) New modified Achilles tendon allograft for treatment of chronic patellar tendon ruptures following total knee arthroplasty. Arch Orthop Trauma Surg 134:713–717

    Article  Google Scholar 

  4. Barrack RL, Stanley T, Allen Butler R (2003) Treating extensor mechanism disruption after total knee arthroplasty. Clin Orthop Relat Res.

  5. Bates MD, Springer BD (2015) Extensor mechanism disruption after total knee arthroplasty. J Am Acad Orthop Surg 23:95–106

    Article  Google Scholar 

  6. Buller LT, Warth LC, Deckard ER, Meneghini RM (2020) Extensor Mechanism Reconstruction Using Marlex Mesh: Is Postoperative Casting Mandatory? J Arthroplasty 35:3747–3753

    Article  Google Scholar 

  7. Burnett RS, Berger RA, Paprosky WG, Della Valle CJ, Jacobs JJ, Rosenberg AG (2004) Extensor mechanism allograft reconstruction after total knee arthroplasty. A comparison of two techniques. J Bone Joint Surg Am 86:2694–2699

    Article  Google Scholar 

  8. Carlson Strother CR, LaPrade MD, Keyt LK, Wilbur RR, Krych AJ, Stuart MJ (2021) A Strategy for Repair, Augmentation, and Reconstruction of Knee Extensor Mechanism Disruption: A Retrospective Review. Orthop J Sports Med 9:23259671211046624

    Article  Google Scholar 

  9. Cottino U, Deledda D, Rosso F, Blonna D, Bonasia DE, Rossi R (2016) Chronic knee extensor mechanism lesions in total knee arthroplasty: a literature review. Joints 4:159–164

    Article  Google Scholar 

  10. Crossett LS, Sinha RK, Sechriest VF, Rubash HE (2002) Reconstruction of a ruptured patellar tendon with achilles tendon allograft following total knee arthroplasty. J Bone Joint Surg Am 84:1354–1361

    Article  Google Scholar 

  11. Diaz-Ledezma C, Orozco FR, Delasotta LA, Lichstein PM, Post ZD, Ong AC (2014) Extensor mechanism reconstruction with achilles tendon allograft in TKA: results of an abbreviate rehabilitation protocol. J Arthroplasty 29:1211–1215

    Article  Google Scholar 

  12. Lamberti A, Balato G, Summa PP, Rajgopal A, Vasdev A, Baldini A (2018) Surgical options for chronic patellar tendon rupture in total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 26:1429–1435

    Article  Google Scholar 

  13. Lim CT, Amanatullah DF, Huddleston JI 3rd, Harris AHS, Hwang KL, Maloney WJ et al (2017) Reconstruction of Disrupted Extensor Mechanism After Total Knee Arthroplasty. J Arthroplasty 32:3134–3140

    Article  CAS  Google Scholar 

  14. Llombart Blanco R, Valentí A, Díaz de Rada P, Mora G, Valentí JR (2014) Reconstruction of the extensor mechanism with fresh-frozen tendon allograft in total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 22:2771–2775

    Article  Google Scholar 

  15. Maffulli N, Spiezia F, La Verde L, Rosa MA, Franceschi F (2017) The Management of Extensor Mechanism Disruption After Total Knee Arthroplasty: A Systematic Review. Sports Med Arthrosc Rev 25:41–50

    Article  Google Scholar 

  16. Mayes WH, Severin AC, Mannen EM, Edwards PK, Barnes CL, Stambough JB et al (2021) Management of Periprosthetic Joint Infection and Extensor Mechanism Disruption With Modular Knee Fusion: Clinical and Biomechanical Outcomes. Arthroplast Today 8:46–52

    Article  Google Scholar 

  17. Nam D, Abdel MP, Cross MB, LaMont LE, Reinhardt KR, McArthur BA et al (2014) The management of extensor mechanism complications in total knee arthroplasty. AAOS exhibit selection. J Bone Joint Surg Am. 96:e47

  18. Ng J, Balcells-Nolla P, James PJ, Bloch BV (2021) Extensor mechanism failure in total knee arthroplasty. EFORT Open Rev 6:181–188

    Article  Google Scholar 

  19. Parvizi J, Gehrke T, International Consensus Group on Periprosthetic Joint I (2014) Definition of periprosthetic joint infection. J Arthroplasty 29:1331

    Article  Google Scholar 

  20. Parvizi J, Tan TL, Goswami K, Higuera C, Della Valle C, Chen AF et al (2018) The 2018 Definition of Periprosthetic Hip and Knee Infection: An Evidence-Based and Validated Criteria. J Arthroplasty 33(5):1309–1314.e2

  21. Poon G, Moo IH, Poon KB (2022) A Modified Surgical Technique of Patellar Tendon Reconstruction in Total Knee Arthroplasty Using Achilles Tendon Allograft. Arthroplast Today 14:22–28

    Article  Google Scholar 

  22. Postler A, Lützner C, Beyer F, Tille E, Lützner J (2018) Analysis of Total Knee Arthroplasty revision causes. BMC Musculoskelet Disord 19:55

    Article  Google Scholar 

  23. Shau D, Patton R, Patel S, Ward L, Guild G 3rd (2018) Synthetic mesh vs. allograft extensor mechanism reconstruction in total knee arthroplasty - A systematic review of the literature and meta-analysis. Knee 25:2–7

    Article  Google Scholar 

  24. Vajapey SP, Blackwell RE, Maki AJ, Miller TL (2019) Treatment of Extensor Tendon Disruption After Total Knee Arthroplasty: A Systematic Review. J Arthroplasty 34:1279–1286

    Article  Google Scholar 

  25. Wise BT, Erens G, Pour AE, Bradbury TL, Roberson JR (2018) Long-term results of extensor mechanism reconstruction using Achilles tendon allograft after total knee arthroplasty. Int Orthop 42:2367–2373

    Article  Google Scholar 

Download references

Informed consent

Written informed consent was obtained from all subjects before the study.


The authors received no financial support for the research, authorship, and/or publication of this article.

Author information

Authors and Affiliations



All authors contributed to key elements of the study design, performed surgeries, data acquisition and interpretation, and submitted manuscript. The authors read and approved the final manuscript.

Corresponding author

Correspondence to Theofylaktos Kyriakidis.

Ethics declarations

Ethics approval and consent to participate

All procedures were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Competing interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Additional information

Publishers Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Kyriakidis, T., Pitsilos, C., Hernigou, J. et al. Satisfactory outcomes of patellar tendon reconstruction using achilles’ tendon allograft with bone block after infected total knee arthroplasty. J EXP ORTOP 10, 12 (2023).

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: