Hemiarthroplasty of the Hip means that only half of the hip joint wil be replaced (hemi = half / partial). Hemiarthroplasties are done for pt.s who have a femoral neck fracture (displaced femoral head) where the blood supply the the femoral head has been comprised. For these circumstances only the femoral head needs replacing, the acetabulum will not be replaced.
A Total Hip Arthroplasty is usually done for arthritis or AVN (AVascular Necrosis). In these procedures both the Acetabulum & Femoral Head will be replaced.
Back to hemiarthroplasties now…
The femoral head can be replaced two (2) different ways, either as UNIPOLAR or BIPOLAR.
In a Unipolar Hemiarthroplasty only the prosthetic femoral head articulates in the acetabulum, only one point of movement (Uni = 1)
In a Bipolar Hemiarthroplasty there are two points of movement (Bi = 2). The prosthetic femoral head that articulates in the acetabulum same as unipolar, and a second area of articulation. Inside the main prosthetic femoral head there will be a second smaller ball that will have articulate as well.
Why the difference?
The decision of whether a patient receives a Unipolar vs. a Bipolar is based on pt age, activity level, & surgeon preference. Any movement there is in a Unipolar, the acetabulum will receive wear & tear. That unipolar head is rubbing directly on the acetabulum. So this type of head is good for older patients that have a very low activity level. Mostly just bed, to chair, & bathroom. With a bipolar, most of the movement is occurring with the smaller ball moving around inside the larger prosthetic femoral head. Once the smaller ball has reached it’s limitations of movement, only then does the prosthetic femoral head articulate with the acetabulum. This extends the life of the acetabulum because there is a decreased amount of rubbing on the acetabulum. Bipolars are done on older patients that have a moderate level of activity (still getting around).
Note…if the patient is young, or is older yet very active, & had suffered an injury that has comprised the blood supply to their femoral head a Total Hip Arthroplasty will be done.
The femoral stem is the prosthesis that holds the prosthetic femoral head in place can be implanted two different ways. The stem will be press-fit or cemented this is determined by surgeon preference.
Note…when doing a cemented femoral stem, it is VERY IMPORTANT to tell anesthesia that you will be cementing. When the cement is placed in the femoral canal it seeps into the porous marrow. The
methylmethacrylate causes cardio & respiratory depression. Anesthesia will closely monitor the patient during this part of the procedure & give the necessary medications to accommodate for the phenomena.
This particular Hemiarthroplasty was done Anteriorly, rather than posterior lateral(3rd pan has Anterior Broaches)
Smith & Nephew Tandem Pan
After the femoral head is removed the diameter is measured in multiple different areas. Whatever the diameter is will be the same size large green ball (femoral head trial) you will choose (ex: if the femoral head measures a 46 diameter, I will select a 46 trial to hand the surgeon). This will be the same whether doing a Unipolar or a Bipolar
On the right side of the pan there a multiple colored pieces these are the Unipolar trials. These will be placed in the underside of the large green balls. Each different color represents a different length, how high or low this trial will sit on the femoral stem. This is important so that the joint is not too tight, too loose, & that leg lengths are similar. For Smith & Nephew Hip Systems the colors are as follows:
– Green = -3
– Yellow= +0
– Red / Brown = +4
– White = +8
– Blue = +12
The gray handles on the right side of the tray are trial impactors (Dr preference to use or not to use. Most of the doc I work with do not use them)
Back of pan in center there is a clamp like instrument. That is used if you need to disengage the locking mechanism in a Bipolar implant. (Rep will explain how to use, hard to articulate the proper technique)
Smith & Nephew EF Spectron Pan
Far back of pan is Box Osteotome to create notch hole in the femoral canal
Left side of pan is the Canal Finder. Goes down the femoral canal to open it up for the broaches
Right side back of pan is the Femoral Broaches. These will be attached to the broach handles located in the center of the pan. The dr will used the broaches in sequence from 1 -5 until, when the broach is fully impacted down there is little to no wiggle movement of the broach inside the femur. After the dr is happy with the size broach, they will detach the broach handle & place a neck trial on the broach. Neck trials are located in the front of the pan on the left side. Neck trials come in STD (Standard) or HO (High Offset). The two necks differ in the fact that the HO trial will push the hip more lateral & will add length to the hip.
Colored heads left side of the pan. These will be the Bipolars trials. The colors represent the length of the trial (as mentioned in the above photo). These will also be plased inside the large green trial head
Front of pan is the Femoral Head Impactor & the Femoral Stem Impactor
Front right beside the necks are the Calcar reamers. Calcar reaming will be done if the trial neck doesn’t sit flush on the femoral broach because bone is in the way.
Smith & Nephew Anterior Broaches & Trials
Back of the pan Anterior Approach Broaches (needs to have an angled broach handle to accommodate for the pelvis being in the way, & not having a straight shot to access the femoral canal as in a posterior lateral approach)
Front of pan Left to right
– Calcar Reamer (see previous photo for. description)
– Femoral Broaches # 1-5 (see previous photo for description)
– Femoral Trials # 1-5 most Dr.s just trial off the broaches (these trials are only STD not HO)
– Starter Rasp (optional) after using the canal finder Dr may want to use this before they start broaching
Because the femoral head is broken off from the rest of the femur dislocating the hip ( displacing the femoral head from the acetabulum) is impossible. After the Dr makes the femoral neck cut & removed the wafer of bone the dr may use the corkscrew (T-handled instrument pictured above) to remove the femoral head. The corkscrew will be malleted in to the 2nd thread, then screwed in the rest of the way. The Dr will use a cobb or hip skid in conjunction with the corkscrew then to lever the head out of the acetabulum.
Front of table is the caliper. This is used after the femoral head is removed to measure the diameter of the head so that you can select a similarly sized trial from the Tandem Pan
Misc Hip Instruments
Left to right
– Narrow Femoral Neck Elevator
– Wide Femoral Neck Elevator
– Large Bone Hook
– Medium Bone Hook
– Canal Finder
– McElroy Curettes x 3 (Sm, Med, Lg)