Orthopedics - Oleksa A.P. 2006

Joint Diseases
Degenerative-Dystrophic Joint Diseases
Primary Chronic Coxarthrosis

The most frequent and severe form of primary osteoarthritis is deforming osteoarthritis of the hip joint (coxarthrosis). According to N.S. Kosynska, patients with hip involvement accounted for 42.7% of all examined individuals suffering from arthrosis, with one-third presenting with bilateral lesions.

As a rule, the disease manifests in both men and women after the age of 50–60, though its clinical course tends to be more severe in women.

The condition develops insidiously and progresses gradually. As noted earlier, the initial signs are a sense of fatigue following walking or prolonged standing. Characteristically, after overexertion, the patient first experiences pain in the knee area, the posterior thigh, or the groin, which can easily mislead the clinician during the diagnostic process. Such pain radiation is most commonly caused by the irritation of the n. saphenus. Upon examination, analgic contracture initially manifests as limited lateral Rotation of the thigh—also an early sign—while restricted abduction is detected only at a later stage. At this point, radiological examination may not yet reveal any pathological Changes in the hip joint. The patient does not yet limp, continues to work, and maintains a normal lifestyle, as pain subsides after rest, and "start-up" stiffness causes little concern.

However, the degenerative-dystrophic process within the joint progresses. As destructive changes advance, pain during walking and movement intensifies and eventually becomes constant. Flexion-adduction analgic contracture of the thigh and marginal osteophytes severely restrict hip mobility, resulting in functional shortening of the limb and lateral rotation. This, in turn, causes pelvic tilt and increased lumbar lordosis. Radiographically, classic marginal ossicles appear, projecting from the margins of the acetabulum, and subsequently forming "beak-like" growths near the Cartilage and the lower part of the deformed femoral HEAD. Already In the second stage of the disease, subchondral sclerosis with cystic radiolucencies in the spongy Bone Structure can be observed.

Despite significant marginal osteoarthritic proliferations and articular cartilage destruction, bony ankylosis of the hip joint never occurs, although the range of motion may be reduced to a minimum, bordering on rigidity.

Furthermore, it should be noted that pathological fractures of the femoral neck due to Osteoporosis do not occur in coxarthrosis. J.H. Healey, V.J. Vigorita, J.M. Lane (1985), O. Moreschini et al. (1995), and R. Oattmeier, J. Babisch (1992) indicate that degenerative-dystrophic changes in the hip joint counteract The Development of osteoporosis in the proximal Femur, and the degree of these changes is inversely proportional to it.

J.H. Healey et al. point out that coxarthrosis acts as a factor that reduces the risk of fractures in this bone region.

P.J. Bilicski et al. (1998) determined the radiomorphometric parameters of the degree of preoperative osteoporosis in unilateral coxarthrosis using the Barnett-Nordin method (Fig. 329) at the level of the Base of the lesser trochanter and 5 cm distally (modified by Zein-Elabdien), as well as Singh's seven-grade scale.

The Barnett-Nordin index is calculated using the formula (AB + CD)x100/AD. The normal value is 40%, osteopenia ranges from 33% to 40%, and osteoporosis is indicated by values below 33%. Bilicski et al. (1988) established that the lowest index values were observed in patients with rheumatoid coxarthrosis.

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Fig. 329. Determination of the degree of osteoporosis according to Barnett-Nordin.

Based on histomorphometry of bone samples harvested intraoperatively from the acetabulum and the proximal femur, Oattmeier and Babisch identified osteopenia in 10% of patients with idiopathic coxarthrosis, 28% with dysplastic coxarthrosis, and 48% with a rheumatoid Etiology. The severity of osteopenia correlates with the stage of coxarthrosis rather than the patient's age or sex.

Treatment. Management of patients with primary chronic coxarthrosis invariably begins with conservative measures.

In the early stage of the disease, the objectives of conservative therapy are: 1) to halt or slow down the progression of the degenerative-dystrophic process; 2) to relieve or reduce joint pain; 3) to restore or improve the function of the affected joint and the limb as a whole.

Conservative treatment encompasses pharmacotherapy, physical therapy, and balneotherapy, as well as limb unloading and the Prevention and correction of contractures. Once the early stage of coxarthrosis is diagnosed, the primary step is to unload the affected joint. Patients are advised to avoid prolonged standing (such as retail workers, service industry personnel, etc.), extended walking, and heavy lifting.

If the patient experiences joint pain after overexertion or presents with analgic contracture, cuff traction of the lower leg is applied for several hours with an individually adjusted weight. Concurrent thermal Procedures (electric heating pads, paraffin-ozokerite Applications, etc.) improve local Blood Circulation and metabolic processes, promote the relaxation of contracted Muscles, and reduce intra-articular pressure and pain, thereby collectively preventing the progression of coxarthrosis. For obese patients, an endocrinologist prescribes a tailored diet to reduce body weight.

To relieve pain, patients are prescribed analgesics and non-steroidal anti-inflammatory drugs (reopyrin, indomethacin [metindol], butadion, ibuprofen, naproxen, brustan). Favorable results are achieved through intra-articular administration of proteolysis inhibitors (trasylol, kontrikal) and biogenic stimulants (arteparon, rumalon, osteochondrin). Every year, an increasing number of novel medications from foreign pharmaceutical companies are introduced and promoted for the treatment of osteoarthrosis.

Triamcinolone acetonide is administered intra-articularly (1 ml every 4–6 days, for a total of 2–3 injections) to inhibit the exudative process. The injection of steroid agents into the joint requires strict adherence to aseptic techniques, even when combined with an antibiotic, to prevent suppuration. Currently, hyaluronic acid substitutes for synovial fluid (such as hylan/hyalgan) and a 15% polyvinylpyrrolidone solution (4–5 injections) are widely used.

Today, there is an exceptionally wide Selection of foreign-made drugs advertised as remedies for osteoarthritis, yet one should not overlook those agents that have proven their efficacy in clinical practice.

In a hospital Setting, attempts have been made to improve joint oxygenation through oxygen insufflation and hyperbaric Oxygen therapy. To enhance local blood circulation and metabolic processes within the joint, patients are prescribed physical therapy and balneotherapy. Novocain Electrophoresis, UHF therapy, paraffin-ozokerite applications, and magnetotherapy provide significant relief to patients.

Sulfur therapy—specifically hydrogen sulfide baths and pelotherapy (muds) in Velykyi Lubin and Nemyriv—along with ichthyol electrophoresis, is considered a pathogenetic method of treating early-stage arthrosis. These treatments normalize thiol groups and sulfur-containing compounds in the cartilage, enzyme activity, and metabolic processes, while extending periods of remission. Comprehensive treatment, including radon baths at the "Khmilnyk" sanatorium and mud therapy in Kuyalnyk, also significantly improves the patients' condition.

Currently, laser therapy and cryotherapy are also widely employed. Laser therapy was first introduced in the former USSR at our department of the Lviv Medical Institute, upon the initiative of Doctor of Biological Sciences Inyushin. By targeting reflexogenic zones with helium-neon laser radiation, local blood circulation and metabolic processes in the joint are improved, and pain is alleviated.

Initial reports on the cryotherapy of rheumatoid Arthritis were published by T. Yamauchi, S. Nogami, K. Miura, and M. Ichise (1983), and it was later successfully adapted for the treatment of arthrosis.

Cryomassage of the joints and cryopuncture using specialized devices (Kovnatsky et al., 1987) exert anti-edematous and analgesic effects. E.V. Pankov applies cryotherapy during arthroplasty for stage II–III arthrosis, which reduces pain and prevents postoperative edema.

The application of these therapeutic modalities helps slow down the progression of arthrosis, preserve the patient's working capacity, and prevent premature disability.

Comprehensive conservative treatment yields good results with prolonged remission, typically in stage I–II arthrosis. If the condition progresses, leading to persistent joint pain and impaired limb function, surgical intervention is then recommended to the patient.

In cases of unilateral coxarthrosis in working-age individuals who are bound to physical labor, hip arthrodesis may be the treatment of choice. Once bony ankylosis is achieved, patients are able to fully bear weight on the leg, lift heavy objects, and perform physical work. This, in turn, unloads the contralateral hip joint and prevents its involvement.

Surgical technique. The Procedure is performed under anesthesia with the patient positioned on the healthy side. The muscles are exposed via an incision of the Skin, subcutaneous tissue, and fascia lata, extending from the anterior superior iliac spine in a semi-arc following the Smith-Petersen approach, passing below the greater trochanter to the posterior margin of the femur. Following blunt Muscle dissection, the hip joint is exposed. The greater trochanter is osteotomized and retracted proximally along with the gluteal muscles.

The Joint Capsule is incised in a T-shape (along the acetabular rim and longitudinally) and excised to the extent feasible.

The femoral head is dislocated, and the destroyed articular cartilage is removed using an osteotome and a reamer. Next, the articular cartilage is excised from the acetabulum down to its cancellous bone structure. The head is reduced into the acetabulum, and the proper adaptation of the coapted surfaces is verified.

It is crucial to position the femur correctly into a functionally favorable alignment. The femur should be slightly flexed (10-15°), and the axis of the limb relative to the intercristal line (linea biiliaca) must be established with the patient in the supine position. Adduction or abduction of the femur must be strictly avoided, as abduction threatens functional lengthening of the operated limb, whereas adduction leads to its shortening.

To achieve absolute immobility of the adapted head within the acetabulum, it can be temporarily fixed with percutaneously inserted Kirschner wires, though ideally, it is permanently secured with two screws or a Smith-Petersen nail inserted from the subtrochanteric region into the ilium at an acute angle so that the fixator does not align with the axis of the femoral neck. Following such fixation, a hip spica cast incorporating a pant leg on the healthy thigh is mandatory.

Nowadays, these Methods have been largely abandoned in favor of fixing the hip joint with a metal fork ("cobra"), the upper two bent ends of which are driven into the supra-acetabular region of the ilium, while the lower portion, shaped as a plate with holes, is fixed with screws to the subtrochanteric region of the femur. In such cases, a plaster cast is not applied postoperatively.

The operation is concluded by drainage and layered closure of the wound.

The wound dressing is changed, and gauze pads are replaced on the following day. Depending on the volume of output during active suction drainage (using a plastic "accordion" or vacuum bottle system), the drain is removed after 48 hours or later. The patient is prescribed strict bed rest for 3–4 weeks.

It should be borne in mind that when the femur is adducted with a fixed metal fork, its upper prongs—driven into the ilium slightly above the supra-acetabular region—may slip out of the bone, leaving the femur in an adducted position and causing functional shortening of the limb. When attempting to abduct the leg, the fork prongs miss the original holes and abut against the ilium, thereby creating a lever mechanism that subluxates or may even dislocate the head. In such events, urgent reoperation is required. To prevent this, some orthopedists apply a hip spica cast with a pant leg on the healthy thigh for 4–6 weeks after fixing the hip joint with the fork. Only thereafter is the patient allowed to get out of bed and use crutches.

In bilateral coxarthrosis among manual laborers, the method of choice may be arthrodesis of the more severely affected hip joint combined with arthroplasty, or preferably, joint replacement (arthroplasty) of the contralateral side. Such patients should be referred to the Medical and Social Expert Commission (MSEC) for disability status determination.

For sedentary workers and those whose occupation does not involve prolonged weight-bearing on the limb, total hip arthroplasty of both joints should be the method of choice. Arthroplasty, as practiced in the past, has proven inadequate because it frequently resulted in residual pain, restricted range of motion, and a non-weight-bearing limb. In Ukraine, Ye. Skliarenko defended arthroplasty for a long time, arguing that "one should not put a person on hinges" when referring to joint replacement. Furthermore, the palliative operations of Fassa and Vent have fallen into oblivion as they provided only short-term relief or were entirely ineffective.

Today, joint replacement is widely employed for both unilateral and bilateral coxarthrosis. Naturally, complications can occur with this surgery, and technical errors occasionally arise; nevertheless, arthroplasty remains the gold standard of treatment today.

Given that coxarthrosis affects the cartilage of both articular surfaces, bilateral (total) hip replacement is indicated in all cases. Antibiotics are administered intramuscularly 24 hours prior to surgery and continued postoperatively.

Surgical technique. The procedure is performed under endotracheal anesthesia with appropriate Anesthetic Management. Regarding the surgical approach to the hip joint, opinions vary. A number of orthopedists utilize the anterolateral Smith-Petersen approach, whereas the majority, both in Ukraine and abroad, favor the posterior Gibson approach, which is technically easier and safer.

In the posterior approach, the tissue incision begins 10–15 cm distal and lateral to the greater trochanter, extending proximally and posteriorly along its posterior border in an arc over the buttock. The muscles are dissected carefully to avoid tissue trauma. In the adipose tissue posterior and medial to the trochanter, the trunk of the sciatic nerve is identified so as to protect it from retractor injury during wound exposure. The short external rotators of the hip are transected near the trochanteric fossa, retracted, and the joint capsule is exposed. The capsule is incised in a T-shape longitudinally and along the acetabular labrum. The leg is flexed and internally rotated to dislocate the femoral head from the acetabulum. The joint condition is visually inspected, periacrtabular osteophytes and adjacent capsule are excised, and the articular cartilage is removed from the acetabulum using an electro-reamer down to the bleeding cancellous bone. Three recesses are drilled into the acetabular walls toward the pubic, ischial, and iliac bones, which are to be filled with "cement" to prevent micro-motion of the acetabular component of the endoprosthesis.

The appropriate size of the acetabular component (cup) is selected to match the prepared acetabulum, as indicated in millimeters on the standard sterile packaging. Next, the bone cement is prepared *ex tempore* by mixing the polymer and monomer, which achieves a dough-like consistency within 2–3 minutes. The acetabulum is filled with the doughy cement, and the acetabular component of the endoprosthesis is carefully impacted into it. Excess cement is removed before it hardens.

The most critical step is the correct positioning (inclination angle) of the cup. The optimal angle of inclination relative to the vertical axis is 45° in the sagittal plane and 15–20° in the frontal plane, which ensures normal weight-bearing and limb function while preventing dislocation.

Once the cement has cured, the level for transecting the base of the femoral neck and removing it along with the head is determined relative to the stem of the femoral component. It is essential to preserve the base of the neck and avoid damaging the lesser trochanter, as it serves as a primary structural support for the prosthesis.

Following this, using appropriately sized rasp-broaches, a canal is prepared in the medullary cavity of the femur for the endoprosthesis stem. It is crucial to form this canal in such a plane that the neck and head of the implanted prosthesis maintain a normal anteversion angle and fit snugly against the bone. The prepared canal is dried, and a thin polyethylene tube is inserted into it to allow blood drainage during the Filling of the canal with freshly prepared bone cement. Afterward, the tube is removed, and the stem of the femoral component is driven into place. Once the cement has set, the prosthetic head is reduced into the acetabular cup, and the site is drained via a polyethylene tube brought out through a stab incision posterior to the wound. The detached muscles are reattached, and the wound is closed in layers. Analgesics are prescribed. Figure 330 illustrates the hip joint following endoprosthesis replacement.

During the patient's transfer from the operating room and throughout the first seven postoperative days, the operated leg must be kept in slight abduction; for this purpose, a pillow-roll is placed between the knees, as dislocations of the prosthetic head can occur during flexion and adduction of the hip. A freshly occurring postoperative dislocation of the prosthetic head can usually be reduced easily, whereas one diagnosed after 7–10 days requires repeat surgery. Postoperatively, the patient is allowed to sit up in bed, and within 10–14 days, to stand and walk with crutches. This is followed by physical therapy (exercise therapy), limb muscle massage, and a comprehensive rehabilitation program. After one month, the patient is permitted to walk using a cane instead of crutches.

Complications following hip arthroplasty. Complications may arise from substandard operating room conditions, intraoperative technical errors, reduced bodily resistance and reactivity of the patient, and The Nature of the microflora.

The most dangerous early complication is surgical site infection (suppuration). It can be superficial or deep, early or late.

The primary sign of a superficial inflammatory process is tissue edema and hyperemia in the wound area. Local hyperthermia may be accompanied by systemic fever. Typically, these are early wound infections. In such cases, several sutures should be removed, the wound edges parted in the hyperemic area, wound contents taken for bacteriological culture, and the surrounding Tissues infiltrated with a broad-spectrum antibiotic solution. If necessary, detoxification therapy and blood transfusions are administered. During daily dressings, the wound—flushed with an antiseptic—is dried, and a dressing with a 0.1% dioxidine solution or 30% dimethyl sulfoxide solution is applied; if indicated, local antibiotic infiltration or a Collagen sponge with gentamicin or vancomycin is utilized.

Superficial wound inflammation can generally be successfully managed, allowing for secondary suture placement and primary healing. Historically, surgical site infections occurred in nearly 11% of arthroplasty cases (Wryblewski B.M., 1984), but this figure has now dropped to 0–1.6% (Chamley J., 1972; Salvati E.A., 1982; Cordero J.G., 1997, and others) thanks to preoperative eradication of infection foci and strict adherence to aseptic techniques.

Fig. 330. Radiograph of a hip arthroplasty.

Deep suppuration may present as early or late-onset. Clinically, it can manifest 4–5 days postoperatively with high fever (up to 40°C), systemic toxicity, localized pain, and tissue Swelling. Occasionally, inflammatory exudate or pus may discharge through the sinus tract after the drainage tube is removed. Staphylococcus aureus and Staphylococcus epidermidis are most frequently isolated, while other pathogens (such as Pseudomonas aeruginosa, Acinetobacter, etc.) are less common. Aspiration may also yield seropurulent exudate, in which case emergency surgery is required. Increasing the dosage and combination of antibiotics can be somewhat helpful, provided there is adequate drainage of the endoprosthesis area coupled with a continuous suction or irrigation system utilizing antiseptic and antibiotic solutions. It is essential to perform bacteriological analysis of wound secretions at least every 5–7 days to determine the microbiological profile and antibiotic sensitivity, adjusting the treatment regimen accordingly. Recently, Bednarek et al. have advocated placing a gentamicin-impregnated sponge instead of postoperative drainage and wound irrigation.

Detoxification therapy and general supportive care for the patient are mandatory. Autovaccine therapy derived from the patient's wound microflora has also proven beneficial.

Thanks to comprehensive and timely treatment, the inflammatory process can occasionally—though rarely—be suppressed and the wound healed. In most cases, however, the endoprosthesis, along with the bone cement and surrounding soft tissues, must be removed, as prolonged conservative management fails and severely debilitates the patient. This surgery should be performed promptly, and necrectomy must be carried out radically within healthy tissue boundaries, particularly in elderly patients, who, despite a hanging hip, can manage with crutches after 2–3 months.

The necessity of removing the endoprosthesis in cases of suppuration is emphasized by Cordero J.G. (1997), Girdlestone G.R. (1993), Wryblewski B.M. et al. (1984), and virtually all modern orthopedic surgeons. Nevertheless, several authors (Argenson J.N. et al., 1997; Buchholz H. et al., 1984; Lindberg L.T., 1984; Gondolph-Zink B., 1997) suggest that in young patients with a short-duration gram-positive infection, revision arthroplasty can be performed shortly after prosthesis removal.

It is important to perform a radical necrectomy simultaneously with the removal of the endoprosthesis and implant a new prosthesis fixed with gentamicin- or vancomycin-loaded bone cement, or use a cementless technique. In such cases, clinical success and complication-free survival at one year have been achieved in 81–90% of patients (Buchholz H.W. et al., 1976; Argenson J.N. et al., 1997; Haddad F., Manktelow A., 1997).

However, the majority of orthopedists initially remove the cemented endoprosthesis, perform a thorough necrectomy, and place a Gentamicin PMMA chain (Salvati E.A., 1984) or a gentamicin-impregnated collagen sponge into the wound, proceeding with cemented revision arthroplasty in a Second Stage. Revision surgery is a highly demanding procedure carrying a risk of recurrent infection, and therefore all potential risks must be carefully evaluated.

Late suppurations occurring months or even years after arthroplasty are typically caused by low-virulence infections (Hope P.G. et al., 1989; Tylman D. et al., 1988, and others).

Alternatively, late deep infection may result from hematogenous seeding from any remote focus of infection in the body (McDonald D.A., 1995; Wryblewski B.M., Deb Sel H.J., 1980). It is particularly crucial to sanitize the Oral Cavity and obtain urine cultures to rule out urogenital infections.

Initial signs of infection are typically insidious rather than acute, and may mimic aseptic loosening of the endoprosthesis by presenting as component instability. Therefore, any loosening requires the exclusion of a potential late infection. In such instances, alongside radiographic and laboratory evaluations, scintigraphy is a highly valuable diagnostic tool (Sanzen L. et al., 1988; Choudhry R.P. et al., 1992; Glithero P.F. et al., 1993; Bohatyrewicz A. et al., 1993).

If suppuration is present, the infected endoprosthesis must be removed, as debridement without prosthesis removal is ineffective. Although Buber H. et al. (1996) suggest that early debridement at the very first signs of infection may salvage the implant without removal.

Regarding revision arthroplasty, it should not be performed as a single-stage procedure in the presence of marked inflammation and purulent exudate.

Following the removal of the endoprosthesis and radical necrectomy, antibacterial therapy is administered for three months—initially via intramuscular antibiotics, followed by oral administration. Only then is the question of revision arthroplasty addressed, although some patients, having adapted to a shortened and dangling limb, ultimately decline the procedure.

Thrombosis and thromboembolism represent the third major postoperative complication. According to Blacha J., Bednarek A., Walawski J. et al. (1998), clinical manifestations of thrombosis in the operated extremity were observed in 5% of arthroplasty patients; however, screening on days 7–14 using color-flow duplex Ultrasonography and phlebography revealed thrombosis in 12% of patients. Four patients developed Pulmonary Embolism post-arthroplasty, of whom one patient died, while the others survived with limited areas of pulmonary infarction.

To prevent thromboembolic events, anticoagulant therapy is prescribed for patients undergoing lower limb surgery.

Superficial vein thromboses are occasionally managed with percutaneous ligation. If further diagnostic imaging reveals a free-floating (flailing) thrombus in the popliteal or femoral vein, the placement of a Cordis vena cava filter via the Seldinger technique in the infrarenal INFERIOR VENA CAVA—with its distal tip secured in the groin—is clinically justified. The filter is flushed three times daily with a heparin solution (5,000 IU in 500 mL of normal saline). The patient continues antibiotic therapy. After 10–14 days, the filter is removed, and anticoagulant therapy is maintained.

The filter prevents detached fragments of a venous thrombus from migrating into the pulmonary artery and Pulmonary Circulation.

Postoperative dislocation of the prosthetic head has been discussed previously and will not be revisited here.

If the acetabulum is insufficiently cleared of cartilage and lacks peripheral bone troughs designed to receive bone cement, the acetabular component (plastic cup) along with its cement mantle may become mobile. Initially, it rotates within the socket, altering its proper orientation; subsequently, it undergoes subluxation, or even complete dislocation, protruding outside the acetabulum. Patients experience joint instability and pain. Once radiological imaging reveals component rotation, surgical intervention is mandatory—even before an overt dislocation occurs—to correct the technical errors made during the initial arthroplasty.

Among late complications, aseptic loosening of the stem is the most frequent, necessitating revision surgery (prosthesis reimplantation). A tight, stable bond between the stem and the femoral bone is directly correlated with a patient's ability to walk freely and painlessly.

Numerous researchers have worked on improving the design of the prosthetic stem to ensure optimal fixation within the femur. Nevertheless, regardless of whether the stem is cemented or cementless, its bone interface is continuously subjected to cyclic mechanical stress that eventually leads to aseptic component loosening, instability, or even a pathological fracture of the femoral diaphysis at the tip of the loose stem.

Consequently, revision surgeries involving the implantation of slightly larger endoprostheses are frequently required today. For femoral diaphyseal fractures, the Kent-type endoprosthesis has proven particularly effective.

Occasionally, revision procedures reveal bone defects of the acetabulum or even the femur. According to the AAOS Classification, acetabular defects are categorized into: 1) cavitary defects; 2) segmental defects; 3) combined bone defects.

To firmly fix the acetabular component of the endoprosthesis, bone or ceramic grafts are used to fill the bone defect. Contained defects are filled with morsellized grafts, whereas large segmental defects are reconstructed using structural grafts secured with screws. Subsequently, the acetabular component of the endoprosthesis is cemented in place. Bone grafts are initially invaded by Blood Vessels and undergo remodeling over a prolonged period.

Occasionally, a bone defect of the acetabular floor is observed, accompanied by protrusion of the acetabular component into the lesser pelvis. Due to prosthesis loosening, the patient may initially experience minimal pain and continue walking, which accelerates the migration of the implant. If revision arthroplasty reveals that the stem of the prosthesis remains stable, the loose cemented acetabular component is removed, the acetabular floor is packed with small bone allografts, and a new gentamicin-loaded cemented cup is inserted. Revision surgery should be performed to restore the center of rotation relative to the contralateral hip, thereby re-establishing the lever arm for the abductor muscles. If the stem is unstable, the entire endoprosthesis must be replaced. Postoperatively, patients are prescribed bed rest for up to six weeks, during which they perform physical therapy and gentle joint mobilization. Walking with crutches is then permitted, while full weight-bearing on the affected limb is allowed six months after the surgery.

According to O.I. Rybachuk, L.P. Kukuruza, V.P. Torchynskyi, O.M. Sulyma (2001), and V.A. Filippenko et al. (2001), despite the wide variety of proposed endoprostheses, total hip arthroplasty does not reduce the incidence of complications, which ranges from 10% to 15%, and can reach up to 40% in the long-term period.

Among the most severe complications is aseptic loosening of the endoprosthesis components, which can be classified as early (occurring within 5 years postoperatively) or late.

Today, all the causes of endoprosthesis loosening following arthroplasty are well-documented. These include:

1. Osteoporosis of the femur and pelvis of any etiology.

2. Incorrect sizing of the endoprosthesis components.

3. Use of endoprostheses manufactured from Materials that fail to comply with the ISO 5832 international standard.

4. Non-compliance with cementation protocols and an insufficient amount of bone cement.

5. Malorientation of the prosthetic cup (inclination angles, depth of insertion) and the femoral component (degree of anteversion, lack of reliable bony support, stem length, and positioning, etc.).

6. Premature weight-bearing on the operated limb (within 3 months postoperatively) and physical overexertion.

7. Excess body weight.

8. Underlying medical conditions affecting Bone tissue structure (hyperparathyroidism, autoimmune thyroiditis, Graves' disease, etc.).

9. Prolonged use of corticosteroids or Chemotherapy drugs.

Endoprosthesis loosening causes pain and impaired function of the lower extremity. Patients tend to favor the leg, limp, try to minimize weight-bearing on the affected limb, and constantly rely on a cane or crutches.

We observed a female patient under our care who exhibited all signs of instability of the pelvic component of the endoprosthesis, which had changed its inclination angle compared to the immediate postoperative period. Despite our recommendations and conservative supportive therapy, the plastic cup rotated and protruded outside the acetabulum 4 years after the primary arthroplasty. The instability was caused by inadequate fixation of the cup with cement, which failed to adequately fill the bone channels. Revision surgery was performed to achieve secure fixation of the acetabular component.

According to V.A. Filippenko and co-authors, loosening of the acetabular component occurs twice as often as that of the femoral stem; however, five years postoperatively, both components are most frequently found to be loose.

Instability of the endoprosthesis leads to osteolysis in the surrounding bone tissue and heterotopic ossification in the adjacent soft tissues. As a result of osteolysis, pathological fractures of the femur at the level of the stem tip may occur, occasionally leading to protrusion of the acetabular floor and prosthetic loosening.

In all cases of endoprosthesis instability, revision arthroplasty is required, which involves replacing the implant and ensuring its stable fixation.

During the surgery, all ossified tissues and scar tissue must be removed, and the surgeon must determine which specific component is unstable, as the procedure may sometimes be limited to replacing that component alone. Most frequently, however, both Components of the endoprosthesis must be replaced.

Following cementless arthroplasty, the fibrous membrane encapsulating the prosthesis should be excised, as its Cells secrete lysosomal Enzymes that promote further osteolysis and loosening of the stem (Kang Jung Kim, 1994).

After removing the femoral component of the prosthesis, any residual cement must be thoroughly cleared, and the size of the new endoprosthesis is determined. The condition of the acetabulum is also assessed following the removal of the unstable pelvic component.

In cases of significant bone defects, bone grafting using compacted cancellous allograft is performed, combined with the insertion of a cementless femoral component. Bone grafting is also indicated for protrusio acetabuli, replacing a loose cemented plastic cup.

Revision hip arthroplasty should be performed in a timely manner, before extensive bone defects develop, in order to ensure a successful surgical outcome.