Bone Allograft in Knee Arthroplasty with Varus Deformity

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The prevalence of degenerative-dystrophic diseases of the knee joint remains high, as confirmed by data from large epidemiological studies, which attribute 35-40% of all limb joint pathologies to them [1]. This problem is of particular medical and social significance due to the predominance of patients of working age, while the progressive nature of the disease in the long term leads to permanent disability in a significant proportion of patients [2, 3].

The "gold standard" for treating terminal stages of gonarthrosis is total knee arthroplasty (TKA). A key intraoperative task, on which the long-term result directly depends, is the adequate restoration of bone defects in the support zones of the endoprosthesis components. According to data from modern registries, the frequency of significant bone defects during primary TKA reaches 30-45%, and in patients with severe varus deformities, this figure exceeds 60% [4, 5]. Despite the existence of various strategies for their management, including the use of bone cement, metal augments, and autografts, each has significant limitations related to durability, biomechanical properties, or the risk of donor-site complications [6, 7].

The techniques and long-term outcomes of using structural allografts in revision TKA are currently well-described in the literature [8]. However, in our opinion, based on an analysis of recent publications in the PubMed and Scopus databases over the past 5 years, the problem of their rational use specifically in primary arthroplasty in patients with severe varus deformities and critical defects of the medial tibial plateau remains insufficiently covered. In particular, there is a lack of unified preoperative planning algorithms focused on CT assessment of such defects and clear criteria for choosing between an allograft and standard metal augments in this clinical situation [9, 10].

Thus, the knowledge gap that this clinical case aims to fill is the absence of clear, standardized solutions for managing complex bone defects in primary TKA, where standard methods may be suboptimal. The rationale for describing it is the need to demonstrate an effective and reproducible surgical approach that allows for anatomical reconstruction and stable implant fixation in conditions akin to revision surgery. The practical significance lies in the fact that the presented case clearly illustrates the possibility of using a biologically and biomechanically sound allografting technique for the radical correction of a severe deformity, which ultimately contributes to increased implant longevity and improved functional outcomes in this challenging patient category.

Patient A., 60 years old. Diagnosis: Bilateral post-traumatic gonarthrosis grade 4 with pain syndrome and limited range of motion.

Upon admission, the patient presented with a varus deformity of the knee joint. For objective assessment, radiography of the lower limbs was performed. The analysis revealed a complex pathology: Fig. 1.a, Fig. 1.b.
Angular measurements confirmed a combined varus deformity: the mechanical lateral distal femoral angle (mLDFA) was 100° (normal: 85–95°), and the medial proximal tibial angle (MPTA) was 74° (normal: 87–90°).
On the tibial side, a marginal bone defect was identified in the medial compartment.
Thus, the case was characterized as complex, due not only to the two-component deformity but also to the presence of a bone defect.

To restore the biomechanics of the knee joint and create a long-term, reliable support for the endoprosthesis components in this patient with a tibial bone defect classified as AORI type T2A, we developed a surgical algorithm utilizing allograft reconstruction.

After performing a standard medial parapatellar approach and staged soft tissue release, preliminary correction of the varus deformity with balancing of the joint space was performed. Then, reference cuts of the tibia and femur were made according to the protocol for the specific endoprosthesis model.

During the intraoperative assessment after placing the trial components, a final evaluation of the bone defect of the medial tibial condyle was conducted. The defect was meticulously prepared: remnants of sclerotic bone tissue were removed until signs of a viable bone bed ("bloody dew") appeared. A structural allograft was selected and shaped to match the form and size of the resulting defect Fig. 2.
The prepared graft was fixed using two or three small-diameter compression screws, with mandatory counter-sinking of the screw heads below the level of the bone surface. After placing the allograft, the trial tibial component was reinserted to check the stability of the construct and assess the correction of the limb axis. Only after achieving optimal stability and soft tissue balance were the final endoprosthesis components implanted Fig. 3.

Control radiography in the early postoperative period demonstrated satisfactory positioning of the endoprosthesis components and complete correction of the pre-existing deformities:

• The mechanical lateral distal femoral angle (mLDFA) was 90°.

• The medial proximal tibial angle (MPTA) was 90°. Fig. 4.a, Fig. 4.b.

The achieved angular parameters indicate complete restoration of the biomechanical axis of the right lower limb.
To ensure consolidation of the allograft and prevent its displacement, a protected orthopedic loading regimen was established. The patient was recommended to use crutches with complete exclusion of axial load on the operated limb for at least 3 months, followed by radiological control.

Provided the patient adheres to the protected orthopedic regimen and undergoes full rehabilitation, the prognosis for life and recovery of function of the operated joint can be considered favorable.
The key factor for long-term success is the complete consolidation of the structural allograft with the patient's own bone tissue, a process that takes from 6 to 12 months. The achieved anatomical restoration of the limb's biomechanical axis creates optimal conditions for even load distribution, which minimizes the risks of aseptic loosening and component subsidence in the long term.

This clinical case illustrates a method for addressing an extensive bone defect of the medial tibial condyle during primary knee arthroplasty. The relevance of this case is due to the persistent uncertainty in choosing the optimal reconstruction method for AORI type 2-3 defects, where standard approaches, such as metal augments and extended stems, have known limitations [1].

(a) Novelty of the observation. In the context of this case, we do not claim a fundamentally new method; however, we clearly demonstrate the effectiveness and technical nuances of using a structural allograft in primary arthroplasty complicated by severe varus deformity. While most publications focus on revision surgery, our experience highlights the potential of this technique for solving complex primary cases, which is less thoroughly described [2].

(b) Results consistent with the literature. Our data are fully consistent with a number of studies that recognize the biological advantages of bone allografting as a gold standard. The achieved fixation stability and restoration of the bone stock, which is critical for future revisions, are supported by works where allografts have shown excellent long-term survival [3]. As in our case, these works note a low rate of aseptic loosening and component subsidence due to remodeling and physiological load distribution.

(c) Contradictions with previously published data and their explanation. Our successful short-term results, however, contradict data pointing to risks associated with allografts, such as resorption, collapse, or fixation failure [4]. This contradiction can be explained not by the patient's age, but by the strict patient selection based on defect morphology (a localized defect suitable for mechanically stable graft fixation), the absence of systemic risk factors (such as osteoporosis, smoking, diabetes), and meticulous surgical technique (precise bed preparation, stable screw fixation). While metal augments are positioned as a more predictable solution, their main drawback—the inability to restore bone mass—makes biological reconstruction strategically more advantageous from the standpoint of preserving anatomy for potential future revisions.

Alternative explanation and uncertainty. An alternative interpretation of the good result could be the correct component placement and restoration of the axis itself, where the allograft played only a supporting role. However, the severity of the defect makes this unlikely. Despite the success, uncertainty remains regarding the long-term fate of the graft. Whether it will be fully revascularized and integrated, or will undergo partial resorption over time, remains an open question and requires long-term follow-up.

Recommendations. Based on this case, structural allografting can be recommended as a viable alternative for patients with localized massive AORI type 2-3 defects, provided they have a satisfactory general health status and bone quality. Key prerequisites are adequate surgical expertise and access to a high-quality bone bank. Nevertheless, further comparative studies with long-term follow-up are needed to definitively determine the place of this technique in the arsenal of an orthopedic surgeon relative to more standardized metal constructs.

This clinical example confirms that the use of a structural allograft in primary knee arthroplasty with severe bone defects is a highly effective strategy. The key advantage of the method lies in its biological nature—the graft does not merely replace the defect but serves as a scaffold for revascularization and subsequent remodeling into the patient's own bone tissue. This not only restores bone stock, which is critical for potential revision interventions, but also ensures a more physiological load distribution compared to metal augments.

Furthermore, the technique creates a stable peripheral bone support, effectively counteracting rotational and axial forces, which prevents implant migration and subsidence. Thus, allografting demonstrates a comprehensive solution that combines biomechanical and biological advantages and is a reliable alternative to the use of extended stems and metal augments, especially in cases of extensive defects.

About the authors

Daniil Yakovchuk

Federal State Budgetary Educational Institution of Higher Education Kazan State Medical University of the Ministry of Health of the Russian Federation

Email: daniilyakovchuuk@gmail.com
ORCID iD: 0009-0008-5632-0229

Ildar F. Akhtiamov

Kazan State Medical University

Email: yalta60@mail.ru
ORCID iD: 0000-0002-4910-8835
SPIN-code: 6579-8640

postgraduate student

Russian Federation, 49, Butlerova str., Kazan, 420012

Sergei Alexandrovich Ardashev

Email: ardashev-sergei@mail.ru
ORCID iD: 0000-0003-4847-2392
SPIN-code: 4948-4406

Akhmad R.H Abukbash

Email: ahmadabukbash929@gmail.com
ORCID iD: 0009-0002-2581-664X

Sergey N. Kalinov

Author for correspondence.
Email: kalinov.03@inbox.ru
ORCID iD: 0009-0000-1975-5313

References

Supplementary files