Total Hip Acetabular Screw Placement

Utilizing acetabular screws in total hip arthroplasty is controversial. Screws can compress the cup and close any gap. Screws could be helpful in osteoporotic bone and when the bone coverage is not sufficient. Screws and its holes can be conduit for migration of polyethylene debris that can cause osteolysis (The surgeon should insert the least number of screws).

Many surgeons prefer to use screws in the acetabular cup. The quadrant technique is a safe technique of screw placement. It provides the surgeon with a simple, basic guide during surgery for safe placement of the screws during the primary and revision surgery.

In order to find the safe zone for the placement of acetabular screws and avoid the danger zone, you will need to draw a line from the Anterior Superior Iliac Spine (ASIS). Then you will draw a second line, perpendicular to the first line. Drawing these lines will divide the acetabulum into four quarters. The posterior-superior quarter is considered the safe zone. There is minimal risk to the sciatic nerve, superior gluteal nerve, and vessels. It is important to direct the screws away from the notch. The anterior-superior and anterior-inferior quarters are considered to be the danger zone due to the external iliac artery and vein as well as the obturator nerve, artery, and vein are at risk. The posterior-inferior quarter is considered the caution zone. Placing screws here can be safe if the screws are less than 20mm. There are still several risks when placing screws in this area and these risks include: the sciatic nerve, inferior gluteal nerve and vessels, internal pudendal nerve and vessels.

A retroverted vertical cup will be at most risk for injury to neurovascular structures. The structures can be at risk in a high hip center, which is reamed superiorly ½ the native acetabular diameter. The new hip will have different anatomic zones than what the surgeon might think. The antero-superior and the antero-inferior quadrants are positioned in the postero-superior quadrant (Be aware of the shift in the zones). The insertion of the screws as guided by the quadrant method is based on a study done by Dr. Ray Wasielewski and his colleagues. When in doubt, aim the screws anteriorly to the greater sciatic notch. The bone will be stronger and thicker. Screws longer than 35mm are usually not needed. Avoid drilling eccentrically because it may lift up the liner. The screw must be fully seated and the head of the screw should not be proud. If the screw is proud, the liner may not be seated properly.

Vascular injuries occur more in females and more often in the left hip.

Tibial Plateau Fracture Balloon Osteoplasty

A tibial plateau depression fracture occurs when axial forces from the femoral condyles against the articular surface of the tibia cause the injury. The compression fracture may also be associated with other fractures. Several techniques are used for the treatment of this fracture. Balloon osteoplasty is proposed as a useful tool for reduction and elevation of the tibial plateau depression fracture.

The technique of balloon osteoplasty can be done with or without the supplementation of screws and plate fixation. Trajectory lines are drawn on the medial side of the knee for access to the fracture area. A small incision is made at the point where the lines cross. A cannula and trocar tip stylet is used to access the fractured area under radiographic guidance. The cannula and trocar is advanced under the area of depression using a mallet or drill when needed. Once inserted, the trocar is then removed from the cannula.

 The precision drill is then inserted into the cannula and advanced until it passes under the depressed area of bone. Then, the precision drill is removed from the cannula and the inflatable bone tamp is inserted through the cannula to the area of the depressed fragments. The inflatable bone tamp is centered under the area of depression and then inflated to reduce the depression fracture. Once the depression has been adequately reduced, the inflatable bone tamp can be deflated and removed from the cannula.

The void that has been left by the inflatable bone tamp is now ready to be replaced with bone filler. The device loaded with injectable material is inserted and used until the void is completely filled. Finally, you will remove the injectable material device and the cannula. Plate fixation may be added before or after the injectable material is inserted.

Gout, Arthritis and Joint Pain

The most common joint affected by gout is the 1^st metatarsophalangeal joint. The most common joint affected by pesudogout is the knee joint (Figure 1). Gout and pseudogout are similar problems with different causes.

Gout is caused by the buildup of uric acid and the deposit of uric acid crystals inside a joint. The best test to diagnose gout is with a joint fluid analysis. Elevated uric acid is not a good criteria. 90% of patients suffering from gout are men between the ages of 40-60 years. Gout crystals are needle shaped and negatively birefringent. When placed under polarized light they will be yellow (Figure 2).

Uric acid builds up the body by two main mechanisms. These two mechanisms are excessive urate production and diminished urate clearance. Uric acid is produced from the breakdown of proteins inside the body and from the proteins of food that is eaten.

Precipitating Factors:

The sudden attack of gout can be brought on by anything that increases the level of uric acid in the blood such as dehydration, increased consumption of alcohol, eating large amount of meat or seafood, and trauma/surgery.

Diagnostic Testing:

Aspiration and analysis of the joint fluid is the best method for diagnosis (Figure 3). There are blood tests such as white blood cell count, C-reactive protein, erythrocyte sedimentation rate, and uric acid level that are helpful in supporting the diagnosis if elevated, but if normal, it cannot definitively rule out gout or pseudogout.

Pesudogout or chondrocalcinosis is the deposition of calcium pyrophosphate dehydrate crystals in the hyaline cartilage or fibrocartilage (CPPD). Pseudogout is a metabolic disease where calcium pyrophosphate dehydrate crystals (CPPD) are formed within the joint space. It most often affects the knee and occurs more in older patients. It is a calcification of fibrocartilage (chondrocalcinosis). Pseudogout crystals are rhomboid shaped and positively birefringent. Crystals will be blue when placed under polarized light (Figure 4). Associated conditions are hyperparathyroidism, rheumatoid arthritis and gout.

Gout and pseudogout both show a sudden onset of pain, redness and swelling typically affecting a single joint in 80% of the cases. Gout symptoms include joint pain, swelling and arthritis. Patients with gout have periarticular erosions along with the formation of uric acid soft tissue masses in and around the joint which can be seen on x-ray. Soft tissue tophus deposition with periarticular erosions called “punch-out” lesions (Figure 5).

X-rays in pseudogout will show this calcification in the articular cartilage or menisci, with involvement of the patellofemoral joint (Figure 6). Calcifications of the synovium, tendon, and ligaments can also be seen.

Treatment of Gout and Pseudogout:

Acute gout can be treated with indocine and colchicine (be aware of peptic ulcer). In cases of chronic gout the patient will be treated with allopurinol (xanthine oxidase inhibitor) and colchicine. Uricosuric drugs such as Probenecid may increase uric acid excretion by the kidneys may be helpful. Pseudogout is treated with NSAIDs and intra-articular injections.

Precious Blood Supply of Bones

There are five major bones with previous blood supply. Fractures in these bones can interrupt this peculiar blood supply, causing a threat of death of the bone and nonunion of the fracture. Fractures in these areas usually occur as a result of trauma or stress related injuries.

These areas are the proximal humerus, scaphoid, proximal femur, talus, and fifth metatarsal. Interruption of the blood supply causes death of the bone and nonunion.

 

There are three types of fractures at the fifth metatarsal; avulsion fracture, Jones fracture, and mid-shaft fractures. The avulsion and mid-shaft fractures have good healing due to a sufficient blood supply. The Jones fracture compromises the blood supply which leads to nonunion of the fracture. Treatment can be achieved by non-weight bearing immobilization or may require intramedullary screw fixation in athletes and active individuals.