Arthrodesis                                                                                                   

Arthrodesis

Arthrodesis is a type of ankylosis involving surgical fixation of a joint by procedures designed to promote fusion of this joint surfaces through promotion of the proliferation of bone cells. It circumvents the pathologic processes by total surgical ablation of the affected joint and assures that it will be stable and pin free.

The development of osteoarthritis in high load-low motion joints such as the equine proximal inter-phalangeal joint is felt to be the result of repeated trauma to the periarticular soft tissues. A currently recommended treatment for this disease is arthrodesis of such joint.

Return to function following non-surgical treatment using electrical stimulation or external coaptation and confinement are often significantly prolonged.  Surgical methods of arthrodesis as a treatment for osteoarthritis or traumatic injury include  curettage of articular cartilage   of  the joint   or   drilling  of  subchondral  bone  incombination  with AO/ASIF cortical lag screw fixation or T-plate placement followed by cast immobilization.

In most cases, arthrodesis is carried out to salvage valuable breeding stock. There are certain joints that can be fused without unduly compromising the animal performance. Such horses can return to comfort and some to athletic soundness after arthrodesis of the proximal interphalangeal joint. 

Arthrodesis are performed in low motion joints especially pastern joint for a return to performance in situations where treatment of arthritis is not successful or in which, treatment has gradually become overpowered by the progression of the degeneration.

ndications of pastern joint arthrodesis

 That, arthrodesis is an elective surgical procedure to eliminate motion in a joint by providing a bony fusion to relieve pain, provide stability, overcoming postural deformity resulting from neurologic deficit and to control advancing disease.

The most common indications for arthrodesis in veterinary medicine divided into traumatic, developmental and congenital. Traumatic injuries to joint consists of both fractures and ligamentous disruptions with or without dislocation, in which a primary repair lead to chronic instability or degenerative joint disease (DJD) and pain. The major developmental diseases can be included under the heading arthritis that further subdivided into idiopathic or secondary DJD, septic arthritis and immune mediated arthritis.

Arthrodesis of the proximal interphalangeal joint (PIPJ) is used in treating degenerative joint disease (DJD), luxations, subluxations and fracture of proximal and middle phalanges. Osteoarthritis or DJD as a disease of diarthrodial joints comprising destruction of articular cartilage to varying degrees, accompanied by subchondral bone sclerosis and marginal osteophyte formation. Synovitis and joint effusion were associated with the disease.

The development of osteoarthritis in high-load low motion joints such as the equine PIPJ is felt to be the result of repeated trauma to the periarticular soft tissues.  Septic arthritis, DJD and rheumatoid arthritis may result in joint instability and pain. Arthrodesis is the only solution when medical or conservative surgical means prove unsuccessful.

The non-surgical treatment for osteoarthritis especially the articular type has been unsuccessful but ankylosis relieves pain by preventing joint movement. Arthrodesis is recommended in case of  acute joint disruptions noted with fractures of the proximal and middle phalanges.

The primary neurological indications of arthrodesis is irreparable peripheral nerve injury resulting in loss of function in the extremity joint and not amenable to a nerve transfer procedure. They added that the function of the limb should be determined prior to surgery by a neurological examination of the limb and evaluation of the animals use of the limb with the affected joint in a  temporary splint.

Orthopedic indications for an arthrodesis include chronic instability or subluxation not amenable to reconstructive procedure, painful arthritis not responsive to medical therapy and certain fractures of the middle phalanx that don’t involve the distal inter-phalangeal joint. Arthrodesis is also indicated for the treatment of severe ligament sprains, severe joint trauma and intra-articular fractures.

PIPJ arthrodesis was performed in individuals with chronic ring bone and subsequent debilitating lameness or in cases of acute trauma to the middle phalanx in which the severity of the fracture necessitates joint fusion to restore a weight bearing bony column, osteochondritis dessicans (OCD), subchondral cystic lesions  phalangeal deviations in foals and flexural deformities. Lameness caused by DJD of pastern joint and comminuted middle phalangeal fracture had been treated successfully in horses by surgical arthrodesis.

Techniques of surgical arthrodesis

Arthrodesis are routinely done in veterinary medicine by either intra-articular or extra-articular means, the former is done when fusing peripheral joints after debriding the joint cartilage, grafting and stabilizing, while the latter is performed on the spine (vertebral column) when short or long segment of spine are bridged with bone to provide stability to entire segments of the spine.

 Most non surgical treatment of osteoarthritis especially the articular type had been unsuccessful but ankylosis relieves pain by preventing joint movement, medical treatment of DJD was usually palliative at best. The condition eventually became unresponsive to all medical therapy unless the condition is so far advanced that spontaneous arthrodesis / ankylosis had occurred.

Prior to the development of prosthetic joints for human beings, arthrodesis is a common surgical procedure for osteoarthritic joints in various parts of the body. The surgical principles that were necessary to achieve arthrodesis of joints include the removal of all articular cartilage and sub-chondral bone until bleeding subchondral cancellous bone was reached. They added that the subchondral cancellous surfaces were approximated and bound by rigid internal implants. Autogenous cancellous bone graft was desirable in any defect between the two opposing bones which serves as a scaffold for ingrowth of new vessels from each of the opposing bones.

The articular cartilage of opposing bones should be removed for achievement of an effective arthrodesis in the shortest time . If the bone ends are sclerotic as a result  of a diseased process they must be removed to achieve formation of new tissue in the defect and good ankylosis. The cartilage was not removed from the proximal interphalangeal joint (PIPJ) during the experimental procedure. It has been proposed that removal of cartilage will alter the radii of the opposing bones.The distal end of the proximal phalanx will be reduced and the proximal end of the middle phalanx will be decreased following curettage of articular cartilage. Although cartilage removal is strongly recommended for arthrodesis to progress rapidly in the clinical cases.

Any defect not filled with cancellous bone would first filled with fibrous connective tissue, then changed into osteoblastic tissue, thus delaying complete ankylosis and external support is required until radiographic evidence of early fusion is seen.

The use of an autogenous cancellous bone graft can substantially reduced the time of osseous union following arthrodesis. However, the presence of cancellous bone between the proximal and the middle phalanges can adversely affect the degree of contact between the subchondral plates.

Using a joint drilling procedure, the articular cartilage can be removed and the joint is then packed with cancellous bone harvested from a different sites. Other techniques of arthrodesis employ a more radical approach to the joint utilizing a variably shaped skin incision and a transection of the dorsal joint capsule of the pastern joint and curettage of articular cartilage followed by support of the joint in a fiberglass cast. Alternatively, the method of lag screw fixation either in criss-crossing or paralled procedure.

Surgical arthrodesis has an overall success rate of about 80%. The current recommended surgical arthrodesis technique which involves placement of three drill holes across each joint of distal tarsal joint, is associated with minimal post-operative complications and pain.

Different methods of arthrodesis of the PIPJ have been described and include curettage of articular cartilage  (Figs 1, 2, 3, 4 ) , insertion of lag screws either by paralled or criss-crossing procedure, application of a dynamic compression plate (DCP) or specially designated T-plate, sliding grafting technique  and combinations of the above methods. All techniques are completed after removing articular cartilage and all involve the use of post-operative cast (Figs 5, 6, 7, 8, 9, 10, 11, 12, 13, 14) .

Surgical methods of pastern arthrodesis as a treatment for osteoarthritis or traumatic injury include curettage of the articular cartilage or drilling of the subchondral bone in combination with cortical screw fixation with lag effect or T-plate placement followed by immobilization. They added that, immobilization without complete curettage of cartilage lead to ankylosis without osseous union.

The principles of internal fixation and fracture repair suggest that rigid compression and fixation with resection of infected tissue and appropriate local and systemic antibiotic therapy in a case of septic arthritis could result in osseous union and successful outcome. He added that as arthrodesis appears similar to long bone fracture fixation, these principles should be applicable to surgical therapy of septic arthritis of the PIPJ.

Several methods of internal fixation have provided successful fusion of the PIPJ after exposure of joint surfaces and curettage of the articular cartilage, two screws in a cruciate orientation inserted with lag effect , three screws placed with lag effect in parallel orientation , a single T-plate  and one or two dynamic compression plate (DCPs) placed across the dorsal aspect of the joint.

Arthrodesis of the PIPJ was recommended as the best method of treatment of comminuted fractures of the middle phalanx by application of a T-plate , a narrow dynamic compression plate, use of a broad dynamic compression plate or two narrow dynamic compression plate.

Fusion of the PIPJ in horse was done by drilling from the lateral aspect of the joint and packing it with a cancellous bone graft while,  used the electrically stimulating fragmented ends after arthrodesis of the PIPJ to minimize extra-articular bony proliferation and hasten bony union between the proximal and middle phalanges.

A technique for fusion of pastern joint. An incision on the dorso-lateral aspect of the PIPJ between the collateral ligaments and the common (or long) digital extensor tendon was performed. The bit is inserted into the joint from one hole and moved dorsal, palmar and medial as many time as required to ensure the destruction of the articular cartilage and subchondral bone as possible. The same authors in addition to It is  not important to remove bone fragment lifted by drill bit which may help in joint ankylosis.

Other techniques aimed compression of the pastern joint with cortical screws were investigated. They stated that the technique of arthrodesis  begin by exposure of the PIPJ from its dorsal aspect to ensure more thorough removal of the articular cartilage.The common (or long) digital extensor tendon was severed by an inverted V-shape or by a Z-plasty. The joint capsule was transversely incised by sharp dissection. The collateral ligaments were severed to allow exposure of the joint. Following arthrotomy a periosteal elevator is used to pry the joint surface apart for optimal exposure of hyaline cartilage.A curette or drill is used to remove as much cartilage from the bone end as possible.Cortical lag screws were placed in the joint to achieve greater stability and shorten the period of healing.

Comminuted fractures of caudal eminence of middle phalanx  treated  surgically  with  PIPJ arthrodesis that performed by destruction of the articular cartilage and placement of two 4.5mm AO/ASIF cortical screws in a cruciate pattern across the joint.

One of the most description of pastern arthrodesis was utilizing a dorsal approach to the joint. Curettage of articular cartilage and the compression of the joint surfaces by cortical screws through the proximal into the middle phalanx using the lag principle. Who found that placement of three cortical screws crossing the pastern joint nearly parallel to the long axis of the phalanges creates a stronger union during the first 120 post operative days than the diagonal insertion of two screws criss-crossing the joint. While, the latter authors found that the criss-cross procedure would be useful for arthordesis of the PIPJ after the transverse fracture  of  the  phalanx than the parallel procedure because the criss-cross screws penetrate the second phalanx dorsal to the area of the fracture.

An arthrodesis technique using two 5.5mm AO/ASIF cortical lag screws in parallel procedure results in favorable outcome in fore and hind limb PIPJ. The technique has  another advantage of decreased surgical and coaptation time.

Method of lag screw fixation is preferred than the curettage of the joint cartilage followed by support of the joint in a fiberglass cast as a techniques for arthrodesis of PIPJ. The convalescent time and cost of hospitalization can be reduced because the cast can be removed earlier, since the joint is inherently more stable owing to the lag screws. They added that the cast left on for an average of 23 days, after that time, it was removed for radiographic evaluation of the joint, then a cast was reapplied.

Other surgical procedure leading to fusion of the PIPJ  using plates and screws. The joint was  fixed  by T-plate contoured to confirm to the anterior surface of the first and second phalanges. The operated limb was placed in a cast from the carpus or tarsus to the hoof. The horse was rested for a total of 12 weeks.

An experimental arthrodesis of the pastern joint are conducted by application of two pins in cruciate pattern and autologous cancellous bone graft were performed in four adult gelding. The leg was casted for 6 weeks after surgery. Ankylosis of the joint was evident at 50 days and was completed at 120 days after surgery. They concluded that the use of pins and autologous cancellous bone for arthrodesis may be easier than using screws or plates.

The biomechanical characteristics and mode of failure of two different screws techniques (3 parallel 4.5mm cortical screws and 2 parallel 5.5mm cortical screws in lag fashion) in equine PIPJ arthrodesis. They observed that 3 parallel 4.5mm cortical screws placed in lag fashion have been an accepted standard for PIPJ arthrodesis in the horse.Two 5.5 mm screws have been shown here to be biomechanically similar to three 4.5mm screws. They believed that, it is surgically simpler to implant two 5.5mm screws than three 4.5mm screws.

The combination of the paralleled screw technique with a dorsally applied dynamic compression plate for fusion of the PIPJ provides the most stable and secure fixation, minimizing motion, expediting bone remodeling and therefore favoring rapid fusion of that joint.

Chemical Arthrodesis

a. Pastern Joint

Sodium monoiodoacetate  ( MIA ) is a chemical compound  which, when  injected intra-articularly causes a rapid decrease in chondrocyte and intracellular adenosine triphosphate concentrations resulting in inhibition of glycolysis and chondrocyte death. MIA has been used experimentally as a glycolysis blocking agent to create arthritis in rats  guinea pigs, chicken  and horses.

MIA blocks a specific enzyme pathway in chondrocyte metabolism, resulting in chondrocyte death, cartilage necrosis, joint collapse and fusion.

 Arthrodesis of distal tarsal joints by intra-articular injection of MIA which compared favorably with surgical one this technique has been suggested as a simple, cheap and easier than the latter one.

 Chemical arthrodesis can not be advocated in clinical cases because of high complication rate and lack of bony fusion.

A series of three injections of 120 mg of MIA into the pastern joint with 10 days intervals would produce an average 80.5% joint fusion in 3 month with unfused areas of the joint showing potential for fusion. The second and third injections of MIA revealed difficulties not encountered on the first injection. Although the needle was inserted to its maximum depth, high pressure was required to inject into the intra-articular space. A soft tissue swelling from pervious injections increased the distance from the skin to the intra-articular space.

Chemical fusion of the PIPJ using intra-articular injection of  MIA  compares  favorably with surgical arthrodesis that the drug not being currently licensed as a pharmacologic agent for clinical use and the risk of inadvertent transmission of drug into the joint.

Recently, chemical arthrodesis of the PIPJ through intra-articular injection of  120mg  of MIA  has been  introduced  as  a treatment for DJD. Pronounced  synovitis after injection by 12 to 24 hours which is managed with sedation and analgesia with  detomidine  and  phenylbutazone  before  injections.

The use of MIA for arthodesis of the PIPJ and the effect of exercise on the degree of fusion in eight horses. Animals received three injections with 10 days intervals of MIA (60 mg /ml) at a dose of 120 mg into the right or left fore PIPJ, perioperatively, the horse received phenylbutazone and low volar nerve blocks  to relive pain. Horses were randomly divided into non-exercised and exercised groups. Exercise consisted of 20 minutes of trotting 3 days per week for 13 weeks. The horses were killed at 24 weeks, slab sections of the joint were evaluated grossly and radiographically for bony fusion. They found that three horses were excluded from the study after developing soft tissue necrosis around the injection site, septic arthritis and necrotic tendonitis. The remaining horses developed a grade 1 to 4 lameness with minimum to severe swelling in the pastern region. All 5 horses showed radiographic evidence of bony fusion (Figs 15, 16, 17,18, 19) .

B. Distal Tarsal Joint

Osteoarthritis of the distal tarsal joints or bone spavin is the most frequent cause of lameness associated with the tarsus. A curative treatment that reverses the degenerative changes and returns the horse to soundness currently does not exit. The trasometatarsal (TMT) and distal intertarsal (DIT) joints of some horses with sever osteoarthritis will fuse without treatment resulting in a return to soundness but spontaneous ankylosis is an inconsistent and lengthy phenomenon.

Surgical techniques of arthrodesis involve removing varying amounts of articular cartilage using a drill bit  and /or internal fixation was conducted. Nevertheless, surgical arthrodesis is a major procedure that requires general anaesthesia, is relatively expensive and has a convalescence period of up to 12 months. More recently, chemical arthrodesis of the distal hock joints in the horse using intra-articular sodium monoiodoacetate has been attempted.

SMIA is reported to produce a reliable, diffuse and sever insult to the articular cartilage after intra-articular injection. SMIA is a potent inhibitors of glycolysis- dependent chondrocytes and had been used extensivly to produce experimental model of osteoarthritis which will ultimately result in ankylosis. A further possible mechanism by which SMIA may enhance arthrodesis is that results in reduced cartilage chondrone formation. Chondrones are thought to delay the ankylosing process by forming persistent cartilage bridges between the joint surfaces. Therefore reduced chondrone formation may lead to potentially more effective arthrodesis.

Intra-articular injection of sodium monoiodacetate (SMIA)* was evaluated clinically, radiographically and histologically as an agent for induction of  chemical arthrodesis of the distal hock joints in donkeys. The distal hock joints of donkeys received two intra-articular injections of sodium monoiodacetate in the distal intertarsal (DIT) and tarsometatarsal (TMT) joints (50mg/joint) of one hind limb at three weeks intervals. Post injection pain was controlled with administration of phenylbutazone for 5 days beginning 6 hours before injections. All donkeys underwent a gradually increasing exercise program, consisting of walking and trotting beginning one week after the first injection and continuing for 20 weeks. Arteriography was conducted for detection of the alteration in the arterial blood supply after arthrodesis.

All treated joints showed radiographic and histologic evidence of fusion 16-18 weeks after the first injection. Arteriography revealed a hypervascularization with numerous fine arterial blood vessels surrounding the site of arthrodesis (Figs 20, 21, 22) .

The intra-articular injections of SMIA offer a relatively simple, inexpensive and non-invasive procedure for distal tarsal joints arthrodesis in donkeys. SMIA was well tolerated in donkeys pre-medicated with phenylbutazone. 

Prognosis & complications of pastern joint arthrodesis

The success of arthrodesis of the proximal interphalangeal joint was 46% in fore limbs and 83% in hind limbs using a technique involving a three screws in converging pattern. A successful cases of bilateral arthrodesis in the fore and hind limbs.  The success of arthrodesis was  67%  in  the  fore  limbs  and  86% in hind limbs.

Transarticular screws techniques using three paralled 4.5mm screws or two cruciate 4.5mm screws, result of comparison revealed that, the paralled procedure created a functional soundness and a superior union between the first and second phalanges during the first 120 days post-operatively. It was easier than the diagonal insertion of the two  screw crossing the joint,  produced better alignment and was less prone to error in screws placement.

The prognosis for horses having arthrodesis to intra-articular fractures or active sepsis had not been reported in large numbers of cases,however, the prognosis for treatment of fractures that involve only the PIPJ had been assumed to be similar to that for DJD.

The complications following PIPJ arthrodesis in horses include radiographic evidence of navicular disease, degenerative disease involving the distal interphalangeal joint and toe-elevation at the beginning  of the weight bearing.  Other complications related to open reduction and internal fixation include infection, and implant associated lameness.

Implant associated lameness was likely to occur if a screw penetrates distally on the palmar or plantar cortex of the middle phalanx and encroaches on the navicular bone articulation, furthermore, even a properly positioned screw that is too long can cause persistent irritation to the soft tissue structures and result in lameness. Toe-elevation occur due to damage to the deep flexor tendon. The same authors in addition  other complications of PIPJ arthrodesis as low true ring bone, screw breakage, excessive formation of callus and fracture of the small shelf created on the distal end of the proximal phalanx. All which produced continued lameness.

Tthe most significant complications associated with arthrodesis was laminitis in the opposing limb which is influenced by the lack of comfortable weight bearing in the injured limb. Lameness associated with excessive periarticular exostosis and increased period in cast were other complications of pastern joint arthrodesis in horses.

Angiographic pattern after pastern arthrodesis: