Orthopedic Hip And Knee Review | Dr Hutaif Hip & Knee R -...

Polyethylene wear particles are phagocytosed by macrophages, which then release proinflammatory cytokines (such as TNF-alpha, IL-1, IL-6). These cytokines activate osteoclasts via the RANKL pathway, leading to periprosthetic osteolysis and aseptic loosening.

Major criteria for PJI (which are definitive for diagnosis on their own) include a sinus tract communicating directly with the joint, or two positive periprosthetic cultures with phenotypically identical organisms. A single positive culture or elevated biomarkers represent minor criteria.

A tight flexion gap with a balanced extension gap can be addressed by increasing the posterior slope of the proximal tibial cut (which increases the flexion space without significantly affecting extension) or by downsizing the femoral component to decrease the AP dimension. Resecting more distal femur or releasing the posterior capsule only affects the extension gap.

Vancouver B fractures occur around or just below the tip of the stem. B1 indicates a well-fixed stem; B2 indicates a loose stem but adequate bone stock; B3 indicates a loose stem with severely deficient bone stock. Since the stem is loose with adequate bone, it is a Vancouver B2 fracture, which typically requires revision using a long-stem prosthesis.

The direct anterior approach utilizes the internervous plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve) superficially. The deep plane is between the rectus femoris (femoral n.) and gluteus medius (superior gluteal n.).

Patellar clunk syndrome primarily occurs in posterior-stabilized total knees. It is caused by the formation of a fibrous nodule at the superior pole of the patella that engages the intercondylar box of the femoral component during deep flexion and "clunks" out as the knee extends (typically around 30-45 degrees).

ALVAL (Aseptic Lymphocytic Vasculitis-Associated Lesions) is characterized histologically by a prominent perivascular lymphocytic infiltrate. This represents a Type IV delayed hypersensitivity reaction to metal ions (cobalt and chromium) generated by the bearing surface.

Lewinnek's safe zone for the acetabular cup is described as 40 ± 10 degrees of abduction (inclination) and 15 ± 10 degrees of anteversion. Implants placed outside this zone have a significantly higher risk of both anterior and posterior dislocation depending on the specific malposition.

As the knee flexes, the tension in the posterior cruciate ligament (PCL) forces the femur to roll and translate posteriorly on the tibial plateau. This femoral rollback allows for increased flexion before the posterior femur impinges on the posterior tibia.

Elevated serum cobalt out of proportion to chromium in the setting of a non-metal-on-metal bearing strongly suggests mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck taper junction. This results in local adverse tissue reactions.

In a valgus knee, the iliotibial band (ITB) is typically the primary tight structure in extension. The standard sequence of lateral release for a fixed valgus deformity usually begins with the ITB (or posterolateral capsule), followed by the LCL and popliteus depending on whether the tightness persists in flexion or extension.

Squeaking in ceramic-on-ceramic hips is a multifactorial phenomenon, but it is most strongly associated with edge loading caused by component malposition (such as excessive cup inclination or retroversion) and microseparation, which disrupt normal fluid film lubrication.

Lewis-Rorabeck Type II fractures (displaced fracture, well-fixed prosthesis) are primarily treated with open reduction and internal fixation, usually with a laterally applied periarticular locking plate. While retrograde nailing is an option for some fractures, many posterior-stabilized knee designs feature a closed intercondylar box that blocks nail passage.

Internal rotation of the femoral component shifts the trochlear groove medially relative to the extensor mechanism, effectively increasing the Q-angle. This predisposes the patient to lateral patellar maltracking and subluxation. It also results in a tight medial flexion gap.

PMMA acts as a grout, not an adhesive glue. It provides initial rigid fixation by penetrating the trabecular interstices of cancellous bone and creating a robust mechanical interlock once it polymerizes and hardens.

Normally, when moving from standing to sitting, the lumbar spine flexes and the pelvis tilts posteriorly, which functionally increases acetabular anteversion and clears the femur. In a stiff spine, the pelvis cannot tilt posteriorly, leading to a lack of necessary functional anteversion. This results in anterior impingement of the femoral neck on the cup and subsequent posterior dislocation.

A successful single-stage revision heavily relies on the use of targeted, organism-specific antibiotics loaded into the bone cement. If the infecting organism is unknown preoperatively, or if it is a highly resistant pathogen (e.g., MRSA, VRE, fungal), a single-stage exchange is contraindicated, and a two-stage revision with an antibiotic spacer is standard of care.

In the setting of chronic, irreparable abductor deficiency with severe fatty atrophy, direct repairs and muscle transfers have unacceptably high failure rates. To prevent dislocation while allowing a functional range of motion, revising the acetabular construct to a dual mobility bearing is highly reliable and preferred over constrained liners, which have higher rates of mechanical failure and loosening.

Classic Kozinn and Scott criteria established strict contraindications for UKA, including a flexion contracture >15 degrees, varus deformity >10 degrees, ROM <90 degrees, and inflammatory arthritis. An intact ACL is generally required for a mobile-bearing UKA. Weight and age limits have been largely expanded or eliminated in modern indications.

High-dose gamma irradiation breaks molecular chains to create free radicals, which then recombine to form crosslinks, significantly improving wear resistance. However, this process alters the crystalline structure, resulting in decreased mechanical properties, specifically lower yield strength, ultimate tensile strength, and fatigue resistance. This makes HXLPE more susceptible to fracture under high-stress conditions like rim loading.

A knee that is tight in flexion but balanced in extension has an isolated tight flexion gap. Increasing the posterior slope of the tibial cut resects more posterior tibial bone, effectively increasing the flexion gap without significantly altering the extension gap. Resecting more distal femur or releasing the posterior capsule would affect the extension gap.

Increasing femoral offset laterally displaces the greater trochanter, which increases the lever arm (moment arm) of the abductor muscles. A longer abductor moment arm means less muscle force is required to maintain a level pelvis during single-leg stance, which consequently decreases the overall joint reaction force across the hip.

The Lewinnek safe zone for acetabular component placement in total hip arthroplasty is defined as an inclination of 40° ± 10° and anteversion of 15° ± 10°. Placing the cup within this zone has traditionally been associated with a lower risk of postoperative dislocation.

The patient's aspirate results (WBC 2,500 and 75% PMNs) are equivocal/indeterminate for a late periprosthetic joint infection (thresholds are typically WBC > 3,000 and PMN > 80%). In cases of indeterminate results, further testing such as synovial alpha-defensin, synovial CRP, or repeat aspiration is recommended to confirm or rule out infection.

Squeaking is a known phenomenon specific to hard-on-hard bearings, particularly ceramic-on-ceramic. It is most commonly associated with component malposition (e.g., steep cup angle) leading to edge loading, loss of fluid film lubrication, and micro-separation or impingement during the gait cycle.

In the Ficat and Arlet classification of femoral head osteonecrosis: Stage I has normal x-rays but abnormal MRI/bone scan. Stage II shows cystic/sclerotic changes with a normal contour. Stage III is characterized by subchondral fracture (the crescent sign) and early subchondral collapse, but joint space is preserved. Stage IV involves secondary osteoarthritis with joint space narrowing.

A fracture around the stem or just below it is a Vancouver type B. Because the stem is loose (subsided), it is not a B1. Because the proximal bone stock is adequate, it is a B2 (loose stem, good bone). The standard treatment for a Vancouver B2 fracture is revision arthroplasty using a longer stem (often a diaphyseal-engaging splined, tapered stem) that bypasses the fracture, frequently combined with cerclage wiring.

Lateral maltracking of the patella is caused by an increased Q-angle or component malrotation. Internal rotation of the femoral or tibial components, medialization of the femoral component, and lateralization of the patellar button all effectively increase the Q-angle and promote lateral subluxation. Conversely, placing the patellar button slightly medially on the native patella lateralizes the bony patella relative to the trochlea, which IMPROVES tracking. Thus, medialization of the patellar button is the exception.

The 'screw-home' mechanism provides stability to the knee in full extension. Due to the asymmetry of the femoral condyles (the medial articular surface is longer than the lateral), as the knee reaches terminal extension in an open kinetic chain, the tibia externally rotates on the femur. In a closed kinetic chain, the femur internally rotates on the fixed tibia.

Aseptic Lymphocyte-dominated Vasculitis-Associated Lesion (ALVAL) is a type IV delayed hypersensitivity reaction seen in metal-on-metal hip arthroplasty. Histologically, it is characterized by a dense perivascular infiltrate of T-lymphocytes, macrophage accumulation, and varying degrees of tissue necrosis (forming pseudotumors). Multinucleated giant cells with birefringent particles describe polyethylene wear debris, not ALVAL.

While high doses of gamma radiation improve the wear resistance of polyethylene by creating cross-links, it negatively affects its mechanical properties, resulting in decreased yield strength, ultimate tensile strength, and fatigue resistance. This can make the liner more susceptible to fracture or rim damage, particularly in thin liners or edge-loading situations.

Intraprosthetic dislocation is a complication unique to dual mobility cups. It occurs when the small inner prosthetic head dissociates from the larger, mobile polyethylene liner. This can occur due to wear of the polyethylene retention rim over time or iatrogenic damage during closed reduction attempts.

The medial femoral circumflex artery (MFCA), specifically its deep branch, provides the main arterial blood supply to the adult femoral head. It crosses posterior to the obturator externus tendon and anterior to the quadratus femoris. Dissection or release of the quadratus femoris too close to the femur can injure this crucial vessel.

The intraoperative finding of the superior and inferior halves of the pelvis moving independently defines pelvic discontinuity. Reconstruction requires stabilizing the two halves of the pelvis. This is typically achieved with a construct that bridges the defect and provides rigid fixation, such as a cup-cage construct, custom triflange acetabular component, or a highly porous shell used with structural allograft/distraction techniques.

Popliteus tendon impingement is a recognized complication in TKA, often caused by an oversized femoral component or prominent posterolateral overhang of the femoral or tibial tray. The popliteus tendon rubs against the prominent edge during flexion, causing posterolateral knee pain.

Kinematic alignment in TKA aims to co-align the axes of the components with the three kinematic axes of the normal knee, thereby restoring the patient's pre-arthritic native anatomy and joint lines. This approach often results in a joint line that is in mild varus compared to traditional mechanical alignment, and typically relies on measured resections with minimal to no soft tissue releases.

A Constrained Condylar Knee (CCK) implant provides substantial varus-valgus stability through a tall, thick tibial post, but it requires competent collateral ligaments (primarily the MCL) to function without premature failure. When the MCL is completely deficient or absent, a rotating hinge knee is required to provide the necessary coronal plane stability and prevent dislocation.

The treatment algorithm for a persistent flexion contracture (isolated tight extension gap) after standard cuts and removal of posterior osteophytes is to sequentially release the posterior capsule from the posterior femur. If capsular release is insufficient, the surgeon should then recut the distal femur to resect more bone. Recutting the proximal tibia would enlarge both the flexion and extension gaps, requiring a thicker poly, leaving the relative mismatch unchanged.

For massive, irreparable abductor tears following THA, transfer of the anterior third of the gluteus maximus (often along with the tensor fasciae latae) to the greater trochanter is the most widely recognized and reliable salvage procedure to improve gait mechanics, reduce pain, and restore active abduction.

Alpha-defensin is an antimicrobial peptide that is naturally produced and secreted by host neutrophils in response to infection by pathogens. Because it is part of the innate immune response specifically targeting microbes, its concentration in synovial fluid is highly sensitive and specific for detecting periprosthetic joint infection, distinguishing it from aseptic inflammation.

Constrained liners are used in patients with severe abductor deficiency or recurrent instability where other options (like dual mobility) are insufficient. Because the femoral head is locked into the liner, impingement or extreme ranges of motion transmit significant torque and shear forces directly to the liner-cup and cup-bone interfaces. This drastically increases the risk of aseptic loosening and mechanical failure of the acetabular component.

Trunnionosis, or mechanically assisted crevice corrosion, occurs at the modular head-neck junction. It is particularly associated with large-diameter metal heads on titanium stems (which increase the torsional forces at the trunnion). The classic serological profile is a preferential elevation of cobalt over chromium. This leads to an adverse local tissue reaction (ALTR) or ALVAL, presenting as a pseudotumor despite a metal-on-polyethylene bearing.

Alpha-defensin is an antimicrobial peptide secreted by neutrophils in response to pathogens. It is a highly sensitive and specific synovial fluid biomarker for diagnosing PJI. Leukocyte esterase is an enzyme produced by neutrophils, not an antimicrobial peptide itself. CRP, IL-6, and D-dimer are acute-phase reactants or systemic markers.

An opening-wedge HTO inherently tends to increase the posterior tibial slope (due to the triangular shape of the proximal tibia and soft tissue tethers like the MCL) and results in relative patella baja (inferior displacement of the patella relative to the joint line) because the osteotomy is proximal to the tibial tubercle, effectively elevating the joint line away from the tubercle.

A knee that is balanced in flexion but tight in extension requires an intervention that only affects the extension gap. Resecting more distal femur or releasing the posterior capsule will increase the extension gap without significantly altering the flexion gap. Resecting more proximal tibia would increase both gaps symmetrically. Downsizing the femur increases the flexion gap.

Chronic patellar tendon ruptures following TKA are notoriously difficult to treat due to poor tissue quality and retraction. Primary repair (with or without wire augmentation) has a high failure rate in the chronic setting. Reconstruction using an extensor mechanism allograft (often comprising the tibial tubercle, patellar tendon, patella, and quadriceps tendon) or synthetic mesh is the gold standard for restoring the extensor mechanism in a chronic post-TKA disruption.

Pelvic discontinuity is defined by a complete separation of the superior (ilium) and inferior (ischium/pubis) hemipelvis. The definitive intraoperative diagnosis is independent mobility between the two halves. Reconstruction requires bypassing the defect and stabilizing both halves, typically utilizing a highly porous jumbo cup with distraction, a cup-cage construct, or a custom triflange acetabular component. Standard cups or cages alone lack the biological fixation and mechanical stability required to heal the discontinuity.

Inflammatory arthropathy (e.g., rheumatoid arthritis) is an absolute contraindication to UKA due to the systemic, pan-articular nature of the disease, which will predictably destroy the preserved compartments. While Kozinn and Scott originally proposed weight >82 kg and age <60 as contraindications, these are now considered relative or obsolete. Asymptomatic patellofemoral osteophytes or chondrocalcinosis without frank arthritis are not absolute contraindications.

Dual-mobility components consist of a small inner metal or ceramic head that articulates within a larger mobile polyethylene liner, which in turn articulates within the metal acetabular shell. The stability is primarily conferred by the large effective outer diameter of the mobile polyethylene head, which dramatically increases the 'jump distance' (the distance the head must translate to dislocate) and allows for a greater impingement-free range of motion.

In a posterior-stabilized (PS) TKA, the PCL is sacrificed. The tibial post and femoral cam engage during flexion to substitute for the PCL's function. This engagement forces the femur to roll posteriorly on the tibia (posterior femoral rollback), preventing anterior sliding of the femur, improving impingement-free flexion, and maximizing the quadriceps moment arm.

This is a Vancouver B3 fracture: the fracture is around the stem (B), the stem is loose (3), and the proximal bone stock is inadequate (3). Treatment requires bypassing the deficient proximal bone to achieve stable fixation in the intact distal diaphysis using a long, distally fixing fluted tapered modular stem (often with structural allograft) or, in older/sedentary patients, a proximal femoral replacement (tumor prosthesis).

Restoring or slightly increasing femoral offset increases the mechanical advantage (moment arm) of the abductor musculature. By the equation of static equilibrium in the coronal plane, an increased abductor moment arm means less abductor force is required to keep the pelvis level during the single-leg stance phase of gait. This subsequently decreases the overall compressive joint reactive force across the hip.

The clinical picture describes Spontaneous Osteonecrosis of the Knee (SPONK), also known as subchondral insufficiency fracture of the knee (SIFK). It overwhelmingly affects the medial femoral condyle in older females. Recent literature demonstrates a very strong association between SPONK and medial meniscus posterior root tears, which abruptly disrupt hoop stresses, leading to localized articular overloading and subsequent subchondral insufficiency fracture.

Extra-articular deformities of the femur or tibia must be carefully evaluated before TKA. Generally, a coronal plane deformity >20 degrees (or sagittal >20 degrees) too close to the joint cannot be compensated for entirely with intra-articular bone cuts and soft tissue balancing without compromising the collateral ligament insertions or violating the envelope of the joint. These cases typically require an extra-articular corrective osteotomy (often performed as a staged or concurrent procedure).

The classic presentation of flexion instability post-TKA includes recurrent effusions, instability specifically descending stairs (which requires quadriceps eccentric control in flexion), and difficulty rising from a chair. Physical exam demonstrates a loose flexion gap (AP laxity at 90 degrees) while the extension gap is stable. This is often caused by an undersized femoral component, excessive posterior slope, or failure to balance the PCL in a cruciate-retaining knee.

Metal-on-metal (MoM) hip resurfacings generate metal ions (cobalt and chromium) that are primarily excreted by the kidneys. Chronic kidney disease (renal failure) is an absolute contraindication because the patient cannot adequately clear these ions, leading to systemic metal toxicity. Other contraindications include females of childbearing age, severe osteoporosis, and large structural cysts in the femoral head.

The popliteal artery is at greatest risk of direct injury during the flat proximal tibial bone cut. It is tethered closely to the posterior capsule by the fibrous arch of the soleus muscle just distal to the joint line. An oscillating saw penetrating the posterior capsule or an improperly placed posterior retractor behind the tibia can directly lacerate or avulse the artery.

In the setting of an acute hematogenous periprosthetic joint infection (symptoms <3 weeks in a previously well-functioning, well-fixed joint), DAIR is indicated. The success of DAIR is significantly improved by performing a thorough OPEN debridement (arthroscopy is inadequate) and strictly exchanging the modular polyethylene insert. Exchanging the poly allows access to the posterior recess of the knee for thorough debridement and removes bacteria adhering to the poly.

Ideal candidates for isolated patellofemoral arthroplasty (PFA) have isolated anterior compartment osteoarthritis. Strict prerequisites include intact knee ligaments (ACL is crucial to prevent abnormal kinematics and rapid wear), normal tibiofemoral alignment (varus or valgus deformities overload the other compartments leading to rapid failure), and absence of inflammatory arthropathy (which will invariably progress to involve the entire joint).

Manipulation under anesthesia (MUA) is the primary treatment for arthrofibrosis (stiffness) post-TKA after a trial of conservative therapy has failed. It is most successful when performed within the 'window' of 6 to 12 weeks post-surgery. After 12 weeks, the intra-articular scar tissue becomes excessively mature and dense, significantly reducing the efficacy of MUA and increasing the risk of complications like periprosthetic fracture or extensor mechanism rupture.

Patients with a stiff spine cannot accommodate to sitting by posteriorly tilting their pelvis. To prevent posterior dislocation during hip flexion, the acetabular cup must be placed in increased anteversion and inclination.

The popliteus tendon is a primary lateral stabilizer in flexion but not in extension. Releasing it selectively addresses a tight lateral flexion gap without affecting the balanced extension gap.

This patient has an adverse local tissue reaction (ALVAL) or pseudotumor from metal-on-metal wear debris. Definitive management requires revision to a non-metal bearing, typically ceramic-on-polyethylene, accompanied by a thorough synovectomy.

A Vancouver B2 fracture occurs around a loose stem with adequate distal bone stock. It requires revision to a long bypass stem, such as a fully porous-coated or fluted tapered stem, to achieve secure distal fixation.

Patellar clunk syndrome occurs in posterior-stabilized knees when a fibrous nodule forms at the superior pole of the patella. This nodule catches in the intercondylar box of the femoral component during active extension.

Internal rotation of the femoral and tibial components medially displaces the patellar groove and internally rotates the extensor mechanism relative to the tibial tubercle. This increases the Q-angle, leading to lateral patellar maltracking.

For acute periprosthetic joint infection occurring within 4 weeks of surgery with well-fixed components, DAIR is the standard of care. Modular polyethylene exchange is a mandatory surgical step to effectively reduce the bacterial bioburden.

A high-offset stem increases femoral offset (horizontal distance) without altering the leg length (vertical height). This effectively increases the abductor lever arm, thereby increasing abductor tension and decreasing the overall joint reaction force.

Ceramic fracture generates microscopic third-body shards that rapidly destroy non-ceramic bearings. A thorough synovectomy is critical to remove debris, and a new ceramic head (often with a titanium sleeve if the native trunnion is retained) must be used.

In a varus knee, the deep MCL and medial capsule are typically released first along with comprehensive osteophyte removal. If further balancing is needed, the superficial MCL and pes anserinus can be sequentially addressed.

A joint that is loose in extension but balanced in flexion requires tightening of the extension gap exclusively. Adding distal femoral augments addresses this space deficit without altering the flexion gap.

A stiff spinopelvic segment fails to retrovert during sitting, depriving the hip of the necessary functional anteversion to accommodate flexion. To compensate and avoid anterior impingement with subsequent posterior dislocation, the surgeon must place the cup in increased operative anteversion and inclination.

In a valgus knee, the structures on the lateral side contribute variably to gap tightness. The popliteus tendon is the primary lateral stabilizer in flexion, and releasing it addresses isolated flexion gap tightness.

Squeaking in ceramic-on-ceramic total hip arthroplasty is overwhelmingly linked to mechanical edge loading. This phenomenon most commonly results from acetabular component malpositioning, specifically excessive inclination or insufficient anteversion.

This is a Vancouver B2 fracture, characterized by a loose femoral component in the presence of adequate bone stock. The standard of care is revision arthroplasty using a longer cementless stem (often fluted and tapered) that bypasses the fracture site by at least two cortical diameters.

The direct anterior approach (Smith-Petersen) exploits the internervous plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve).

Alpha-defensin is a biomarker naturally produced and released by host neutrophils. It functions as an antimicrobial peptide that helps destroy bacterial pathogens within the joint fluid.

Patellar clunk syndrome is caused by a fibrous nodule forming at the superior pole of the patella. As the knee actively extends from deep flexion, the nodule catches in the intercondylar notch of the femoral component and abruptly dislodges around 30 to 45 degrees of flexion.

Adverse local tissue reactions (ALTR) or aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) in metal-on-metal hips are predominantly driven by a Type IV cell-mediated (T-cell) delayed hypersensitivity response to metal wear debris.

Older flat-on-flat total knee designs suffered from highly concentrated peak contact stresses that propagated below the polyethylene surface. This mechanism caused subsurface fatigue cracks, classically resulting in delamination and pitting of the polyethylene.