(Surgical options for end-stage mechanical failure hip and knee) 

Hip Reconstruction - options

1) Arthrodesis - In young patients with unilateral hip disease (post traumatic) and a good (no LBP) back and ipsilateral knee. A return to normal activity, may be expected with pain relief. Indications are arthritis, failed osteotomies, and failed cup arthroplasty in young patients. A (hip spica) maybe used to show the patient the effect. Position neutral adduction and rotation with 30 degrees of flexion (avoid abduction and internal rotation). Fixation is use of AO Cobra plate (stable but disrupts abductors). Complications include non-union, malposition (most common), degenerative joint disease and instability of the ipsilateral knee, back, and contralateral hip. Can not be done bilaterally but can be done with a contralateral (THR). Later option of conversion to THR Revising a fused hip to THR is difficult and done where painful mal-unions / non-union, and LBP or knees painful or unstable.

Note: marked short leg limp makes it an unattractive option for many young patients.

2. Resection Arthroplasty (Girdlestone) - For incurable infection (especially after failed THR), radio osteonecrosis, or non-ambulation. Shortening of 2-5 cm and severe Trendelenburg gait will need crutches but most can manage with unilateral.

3. Femoral Osteotomy - Common in Europe for advanced OA. For localised structural defects that can be redirected to a nonweight bear area. Technically difficult with hight failure rate that THR - however worthwhile consider in young patients. Image 1. Check x-rays in abduction, adduction and internal rotation to plan for the best correction. Requirements are young nonobese patients with good ROM and x-rays with focal defects. When the femoral head fits better with the head in abduction, a varus or adduction osteotomy is used. When the femoral head is more congruent with the hip in adduction, a valgus or abduction osteotomy is used. Rotational (Sugioka) osteotomies preserve leg length but technically almost impossible.

4. Pelvic Osteotomies (Table 1) - Can redirect acetabular cartilage (Steel, Sutherland, Salter, Dome/Dial) or augment deficient acetabulum with non-articular bone (Chiari, shelf). Redirection osteotomies require a congruent joint early with >50% joint space and >60% ROM left; the Chiari and shelf procedures are salvage ops. (articular cartilage reduced by >50%). See Table 1.

5. Resurfacing Arthroplasty - High failure (20-50% at 5 years) at the femoral neck due to loss of vascular supply. More recent interest in Thrust Plate (hybrid of above and sliding plate).

6. Hemiarthroplasty - Needs a normal acetabulum. (Out for OA). Austin Moore useful in non-ambulators, with poor mental status and limited life expectancy. Bipolar is better option where no OA and better outlook.

7. THR - used for OA when medical treatment failed. Also (RA), osteonecrosis, developmental dysplasia of the hip (DDH), fractures, failed reconstruction, and tumours (Image 2). May consider in young patients with LBP or ipsilateral knee OA (where not candidates for fusion). Conservative therapy, (weight loss, NSAIDs, modification of activity, and use of a cane (in other hand) must be tried first Severe pain with functional disability (limited mobility, night pain) despite therapy, are the principal indications for THR. Contraindications include severe medical problems that can be improved, non-walkers, the skeletally immature and those who cannot or will not understand the rehab. (mentally disturbed), active infection, rapid destruction of bone,

1. Miller MD. Rview of Orthopaedics. Second Edition. Saunders 1996.

neurotrophic joint, abductor mass loss, and progressive neurologic disease. Preoperative checks includes medical and dental evaluation, blood tests and surgical plans. Pre-and postoperative antibiotics are used (important in controlling sepsis), Careful preparation of the patient and the OR to decrease

TABLE 1. PERTINENT FEATURES OF VARIOUS PELVIC OSTEOTOMIES

PROCEDURE OSTEOTOMY DETAIL USE COMMENT

Salter Innominate (open wedge) Youth /anterior deficiency Poor lateral coverage/length

Steel Innominate and both rami Increased dislocation Increased instability, complex

Sutherland Innominate and pubis Can medially displace Less rotation

Dome/Dial Acetabulum subchondral Good cartilage Osteonecrosis and penetration

Chiari Innominate (displaces roof) Salvage Loses cartilage and cartilage continuity (fibrocartilage metaplasia)

infection (laminar flow, surgical exhaust systems, and special drapes may reduce rate of infection). (DVT) prophylaxis pre-operatively is important.

X-rays obtain an AP pelvis film, a cross-table lateral view centred at the hip and an AP view centred at the hip. The quality of the bone is evaluated: and type (Goodman et al).

Type A: Good cortical bone on both AP and lateral views (both veins)

Type B: Good cortical bone one view (anteriorly or lateral).

Type C: No good cortical bone.

Surgical Approach - The anterolateral approach (without a greater Trochanteric osteotomy)l used; the posterior approach is also used (increased incidence of dislocation but surgeon’s choice) probably less limp.

Implants

Femoral Component - Either cemented or non cemented (press fit and/or porous ingrowth) use. Consider metal type and design properties. Stainless steel or supermetal alloys (Co-Cr-Mo) often used, but newer titanium may allow increased implant load transmission to the cement and bone in the calcar region. (Poor wear characteristics led to use of C-Cr heads). Ceramic heads may have less wear. Recent return to metal-on-metal. Aseptic loosening is a problem (loosening in torsion common). Press-fit prostheses rely on bone formation around the stem to allow a tight fit. Porous-coated implants with surface openings of 150-400 am to allow bone ingrowth. Initial stability is by maximum interference fit (with less than 150 microns of motion). Stems not coated distally to allow later revision. Proximal porous coated implants, may decrease stress shielding to the proximal femur (where stress transfer occurs) Not yet clear. complications may involve metal ion release and loosening. Postoperative thigh pain is common. Newer materials, coatings, and designs may allow better results in the future. Hydroxyapatite coatings and fibermesh allow better ingrowth in animal models. Cemented stems are best for older patients (>65 years physiologic age) with poor bone quality (type C bone). Uncemented stems are best for young patients and for revision surgery. Collared designs may have decreased subsidence rates and higher load-to-failure rations. Collar decreases cement stress. Gold standard remains Charnley THR. Bovine (isogenic) implants may be way of the future.

Femoral Head - The smallest (22 mm) allow less stress/torque but may cause increased wear. Larger head sizes (up to 32 mm) allow increased ROM but dislocate. Heads of 26-28 mm are the ideal.

Acetabular component - Cemented or non-cemented use. Placement of screws maybe dangerous (iliac vein is at risk with anterosuperior screws; obturator artery is at risk with anteroinferior screws). Under remaining and press fitting porous coated implants (with-out screws) is non standard.

Acetabular Cup - Use ultra high-molecular-weight polyethylene (UHMWPE). Tilt 10-20 degrees and minimal thickness of 6mm. Orientation is critical for stability.

Position - Femoral should be in slight valgus with 5-10 degrees of anteversion. The acetabular in 10-15 degrees of anteversion and 45 degrees inclination. Acetabulum which are more vertical have increased polyethylene wear and osteolysis.

Complications of THR

Osteolysis - All mechanical devices, including biological with limited capacity for repair, wear out. Wear particles are generated. Current topic of interest. The immune system responds. (Macrophages and gait cells generate PGE₂, collagenous, and humeral factors leading inflammation and resorption of bone at the bone prosthesis interface). Polyethylene particles and those of polymethylmethacralate, titanium and cobalt chrome caused by component shape, contact stresses, material tougheners, and metal fretting.

Osteolysis leads to aseptic loosening - The complication of a cemented femoral prosthesis (based on radiographic and clinical grounds). X-ray basis for loosening (Harris et al) three groups: Definitely, loose component migration, cement cracks, or component fracture. Probably loose radiolucent zones around the entire prosthesis. Possibly loose with radiolucency of more than 50% (a 10-40% incidence of radiographic loosening at 10 years). First to loosen (first 5 years) is the femoral component, at its cement interface; late loosening is the acetabular component. More common with young patients, RA patients, obsess and prior surgery. The diagnosis and treatment of loosening are largely based on the patient’s symptoms. Bone scans not specific. Arthrograms not helpful. Aspiration and culture done to rule out septic loosening. (False negative 15-30%) Treatment for increased symptoms and progressive x-ray loosening (subsidence), surgical.

Stem Loosening - Four types described for cemented hip replacement (Table 2). Cracks most common in the cement mantle on the anterolateral surface of the femoral prosthesis. (Uncemented stems with a porous surface fail if bone does not grow seen early). Late loosening of a well fixed porous coated stem is unusual. See Gruens x-ray zones (Image 3).

Cup Loosening - Three zones (DeLee); I, superior; II, middle; III, inferior. Considered loose if there is a radiolucency >2 mm in all three zones, or change in position of cup (Loosening between the cement and cup is unusual). Non-cemented press-fit acetabulum, with cemented stems (hybrid design), has reduced cup loosening. Related to osteolysis.

Cement technique - Use Canal plugging, reduced cement porosity, canal preparation, cement column pressurisation (third generation cementing technique)

Implant Failure - unusual now.

Stem Failure - In heavy, active patients/varus position of the stem; small stem and long necks; stainless steel and poor proximal support (bending cantilever fatigue). Fracture begins in the middle third of the anterolateral aspect of the stem and progresses medially.

Acetabular Wear -  Wear rates of less than 0.1 mm/year seen (due to UHMWPE); increased with loose prostheses/acrylic debris? Metal backing - may help.

Dislocation - Rate of 1 - 4% of primary THR. Caused by pistoning and malposition. Common with revision THRs. Late dislocation.

Heterotopic Bone - Increased in : males, in ankylosing spondylitis, diffuse idiopathic skeletal hyperostosis (DISH), Post traumatic arthritis, heterotopic osteoarthritis, and previous history. Treat with low-dose radiation therapy (800-1000) cGy (rads) postoperatively and Indomethacin (1 month preop to 3 months postop). Components are shielded.

DVT - Common serious complication cause of postop mortality. Increased with older patients, osteoarthritis (versus RA), history of DVT, obesity, long operations, large blood loss, congestive heart failure (CHF), malignancy, and prolonged immobility. Warfarin the best prophylaxis, also mini - dose heparin, low molecular weight heparin, enteric-coated aspirin, dextran and mechanical pneumatic devices. Present evidence suggests prophylaxis does not work - controversial. B-mode ultrasonography diagnoses (DVT). Ventilation-perfusion (V/Q) scan for diagnosis of pulmonary embolism (PE). Venous filters for high-risk patients.

TABLE 2 MODES OF CEMENTED FEMORAL STEM LOOSENING (After Miller)

MODE MECHANISM CAUSE FINDINGS/RESULTS

I Pistoning Subsidence Stem in cement or cement mantle

II Medial stem pivot Medial migration Proximal medial, distal lateral shift

III Calcar pivot Distal toggle (hold) Windshield wiper effect

IV Cantilever bending Proximal resorption Medial migration, defect, or fracture of proximal stem

Intraoperative Complications - Includes: fracture medial calcar (which is fixed with cerclage wiring/longer femoral stems); neurovascular injury (common peroneal, footdrop); vascular injury from acetabular screws placed anteriorly [superiorly and inferiorly]); shaft penetrations (during revision); Hypotension during cement insertion (complement activation usually transient may be fatal; Ensure hemodynamically stable).

Greater Trochanteric Problems - Less common now with fewer Trochanteric osteotomies used for exposure.

Infection - Catastrophe. Increased morbidity, costs and mortality. Increased with obesity, diabetes, sickle cell disease, osteonecrosis, alcoholism, RA, immunosuppressive drugs (steroids), urinary catheterisation, Long procedures and revisions. Use IV antibiotics, ultraclean air, ultraviolet lights and decreased traffic and conversation in the operating room. Prophylactic antibiotics for dental, oral, GI, GU, and respiratory procedures. Organisms include Staph. aureus (penicillin, cefazolin), streptococcus (penicillin), E. coli (amphotericin ± gentamicin) and Pseudomonas (gentamicin, ticarcillin). Present with pain at rest. ESR and C-reactive protein levels are elevated. A bone scan (indium) and aspiration used. Tissue biopsies (with frozen section confirmation of >5PMNs/high-power field) are useful. Acute infections (first 12 weeks) managed with irrigation and debridement (superficial if definitely not deep by aspiration , leave prosthesis in IV antibiotics for 4-6 weeks followed by orals for 26 weeks. Close follow-up. Deep delayed infections (3-24 months postop) must remove prosthesis and cement; long-term antibiotics. (Exchange arthroplasty for less virulent organisms at several-week delay). Late hematogenous (more than 2 years) follows infection elsewhere. As above and later replacement prosthesis. Recurrence ò 13% (greatest with retained cement and in replantations within 1 year after component removal). For virulent organisms (Pseudomonas) a resection arthroplasty; and antibiotic impregnated cement (vancomycin/gentamicin) (800 mg of antibiotic (gentamicin/tobramycin) is used for 40 grams of cement).

Other Concerns - Nerve injury (sciatic >femoral >obturator - rare with good technique), urinary retention (lowest with preop and 24 hour postop indwelling catheters) (Sciatic nerve injury, traction from excessive lengthening, transient; Femoral nerve injury excessive retraction) from Revision THA - worse results. Pain is the major indication for revision (and impending femoral fracture, recurrent dislocation, and wear of the acetabular cup). Remove hardware and all cement. The revision femoral stem length should be 1-3cm longer. If there is femoral cortical disruption, the revision stem should extend two to three shaft diameters distal to the defect. Bone grafting is often required. (Cemented revisions high failure rate of 10-30% after 5 years). Porous coated implants re-revision rate of approximately 7% after 5 years. Impaction bone grafting (the Ling technique); morselized allograft is packed tightly into the proximal femur followed by implantation,) is now used.

Specific Concerns

Acetabular Defects Classified: I, segmented; II, cavitary; III, combined; IV, pelvic discontinuity; or V, arthrodesed.

Difficult surgery.

Otto Pelvis (Arthrokatadysis) - Primary protrusion in middle-aged women, bilateral in one-third, related to osteomalacia. Bone grafting with femoral head useful.

Note: - Childhood hip subluxation is the most common cause of OA in patients 40 years. Other childhood hip disease that may result in THR are: Perthes disease (SUFE), osteonecrosis, DDH (Image 2)

Knee Reconstruction - Options

Arthrodesis - Indicated where complete joint destruction, usually from severe ligamentous and articular damage neuropathic joint and in failed total knee replacements (post infection). Fusion in 10-15 degrees of flexion and 0-7 degrees valgus is best. Best results from intramedullary fixation with Huckstep Nail. Complications are delayed non-, or malunion.

Osteotomy Where unicompartmental OA of the knee. Transfers weight bearing load to uninvolved tibiofemoral surface. Usually for medial compartment disease or for lateral compartment disease (more difficult).

Medial Compartment OA - Valgus osteotomy of the proximal tibia for medial tenderness, less than 15 degrees of fixed varus deformity, and intact lateral and patellofemoral compartments. Contraindications lateral subluxation of the tibia on the femur >1cm (articular incongruity), tibial subchondral bone loss, flexion contracture > 15 degrees, limitation of flexion beyond 90 degrees, limitation of flexion beyond 90 degrees, peripheral vascular disease, and lateral thrust (high adductor moment). Full length x-rays to assess the mechanical axis of the limb. An upper tibial closing wedge osteotomy held with staples. (Coventry standard) and fibular shortening (or tibiofibular disarticulation) is the Gold Standard. (Overcorrection 2-3 degrees is ideal). Best results in young patients with good bone stock. Problems include undercorrection (most common), overcorrection, penetration of the articular surface, (AVN) of the plateau, patella baja, peroneal nerve injuries, and anterior compartment syndrome. Will last 7-10 years prior to a total knee arthroplasty (TKR). (A TKR more difficult later but possible patellar baja).

Lateral Compartment OA - Varus osteotomy - a medial closing wedge osteotomy of the (supracondylar femur (held with a plate). Used for valgus of >12 degrees and >10 degrees deviation of the knee joint from the horizontal. Preoperative ROM ò 90 degrees, <15 degrees flexion contracture, and no associated instability. Medial displacement of the distal fragment helps.

Debridement - Debridement and drilling with abrasion chrondroplasty, (arthroscopically) temporary help.

Arthroplasty

Unicompartmental Arthroplasty - Patients with single compartment OA who are not suitable for high tibial osteotomy (because of age). Gives a better ROM, preservation of cruciate ligaments and of bone stock. Use in older sedentary patients (not obese) and not in fixed deformities, inflammatory arthritis, anterior cruciate ligament (ACL) insufficiency, young patients, obese patients, dynamic instability. Technique is difficult (overall mechanical axis should fall just over the implant).

Total Knee Arthroplasty TKR for knee pain and disability due to OA/arthropathy (at least two compartments) where failed non-operative treatment. Contraindicated where no knee extensors, severe neuromuscular dysfunction, active sepsis, prior surgical fusion, and in neuropathic joint.

Component Design - Conforming. Linked prosthesis, (fully constrained) (tibial loosening, increased wear and high infection rates. Conforming have condylar metallic femoral components and metal-backed polyethylene tibial. Sacrifice the ACL and some posterior cruciate ligament (indicated for large fixed contractures that require removal of the PCL and in post-patellectomy knees). PCL sacrifice may cause difficulty with climbing stairs. TKR technique (1) horizontal joint in stance phase; (2) restoration of the anatomic and mechanical axes; (Image 4) (3) a flexion gap equal to the extension gap; (4) proper soft tissue balance; and (5) good patellar placement/alignment.

Range of motion - Range of motion postop intra-op ROM (CPM) and manipulations little valve. Atleast 90 degrees of flexion is required to arise from a chair.

Continuous Passive Motion: (CPM)

Increases short-term range of motion may cause patellar tracking problems.

Intra op. technical problems - Table 3.

Complications Table 4.

TABLE 3. Correction deformities during TKR

DEFORMITY USE

Fixed varus Lift medial capsular sleeve, excise medial

osteophytes, deep MCL followed by superficial

MCL

Lateral Release popliteus tendon

subluxation

Fixed valgus Lateral approach, lift IT band, LCL, posterolateral

capsule

Fixed flexion Excise anterior osteophytes, elevate capsule and PCL

release gastrocnemius, ñ posterior capsulotomy

Limited flexion Quadricepsplasty (V-Y) or patella tendon Z-plasty,

or patellar tubercle osteotomy

TABLE 4: TKR COMPLICATIONS (often a nightmare)

COMPLICATION RISK FACTORS RECOMMEND

Infection as discussed

Patella fracture Sacrifice of lateral geniculate artery; Preserve artery

thin/small patella; component poor Minimally displaced fracture;

position Immobilize in extension

Displaced fracture; removal of component and patellectomy

Tibial tray wear Thin (>8mm) components Thicker trays/exchange

Peroneal nerve plasty Flexion contracture/valgus knee Flex knee postop

Supracondylar fracture Anterior femoral notching rheumatoid Avoid notching; ORIF

osteoporosis

Skin slough Poor incisions, (excessive raising of lateral flaps)

Decreased ROM Poor rehabilitation; Manipulation under anaesthesia (long term results un-changed)

Surgical Technique - Correction of deformities is critical (Image 4). Resecting the tibial surface at 90 degrees. Avoiding a notch of the anterior femoral surface. Make proper cuts. Allow proper tracking of the patella. Maximum cover of the tibial plateau. Correct alignment obtained with use of extra- and intramedullary gigs. Trial components. Check flexion and extension gaps. Increased flexion gap (loose in flexion and tight in extension) is common and corrected by resecting more of the distal femur. Increased extension gap (loose in flexion and tight in flexion) is the result of a technical error. Corrected by resecting the posterior sloping surface of the tibia. When tight in flexion and extension, more tibia should b resected. Excessive patellar thickness can result in tightness with flexion and requires additional patellar resection. Pay attention to patellar tracking (superolateral geniculate artery should be kept). Bone grafting where defects involving >50% of the tibia plateau. Preserve bone stock use morrelized bone grafts.

Patella - Controversy Resurface in all cases (especially in RA). Patellar thickness should be restored. Place the femoral component in slight external rotation. Less than 20 mm of patellar thickness is contraindication. No metal-backed patellar components.

Revision TKA - Restore the original joint line. Difficult use the adductor tubercle, the tip of the fibula, and other landmarks. The MCL must be intact to use a nonconstrained prosthesis. Revision implants have more mechanical restraints (higher failure rates from implant loosening, from increased stresses at the bone - cement interface).