Normal Anatomy of the Shoulder
The shoulder is a ball and socket type of joint. The shoulder is like the hip of the upper body. It is where the extremity or limb attaches to the rest of the body. Medically speaking it is known as glenohumeral joint. It is the joint between the head of the humerus (upper arm bone), and the glenoid fossa (shoulder socket, which is part of the scapula/shoulder blade). Note that the clavicle or collar bone is also considered part of the shoulder, but that will not be covered here. A visualization of the shoulder joint can be gained by imagining a fist being placed into an open hand. The fist is the head of the humerus and the open hand is the glenoid fossa. To prevent friction in this joint, there is cartilage on the surfaces of the bones. This is called articular cartilage. Articular cartilage is the smooth, white tissue that covers the ends of bones where they come together to form joints. Healthy cartilage in our joints makes it easier to move. It allows the bones to glide over each other with very little friction.
There are other structures in the shoulder joint which help to give it strength and stability. There is the labrum which acts as a fibrous stabilizing ring around the joint and actually helps to create more surface area within the joint so that the head of the humerus does not slip out of the joint. Also there is a network of ligaments which also serve to stabilize the joint, and the tendons which provide a means for attachment of the muscles which provide movement of the arm and shoulder. Lastly there is the joint capsule wrapping around the joint, and a structure called a bursa which helps reduce friction. Unlike the hip joint, the shoulder joint has a lot more mobility and therefore, it potentially has more instability. The shoulder has many moving parts, and it is a complex joint that requires all parts to operate correctly in order to have a full and pain free range of motion.
Injuries and Problems of the Shoulder Joint
The shoulder joint is vulnerable to stress, traumatic injury, overuse, and arthritis. The articular cartilage in the shoulder can be damaged by injury or normal wear and tear. When it is damaged, the joint surface may no longer be smooth. Moving bones along a tough, damaged joint surface is difficult and causes pain. Damaged cartilage can also lead to arthritis in the joint. Articular cartilage does not heal itself well, so sometimes surgical intervention is required.
Types of Surgical Interventions for the Shoulder
There are several different options when it comes to shoulder replacement surgery. Your surgeon will discuss with you the best option for your particular condition.
Total Shoulder Replacement
This is the most common type of shoulder replacement surgery. It typically uses metal and plastic replacement parts to repair the joint. The procedure involves surgical removal of head of humerus, and smoothing and reshaping of the shoulder socket (glenoid fossa). A plastic part called the glenoid component is inserted into the smoothed out socket. This glenoid component is held into place with bone cement.
Note: Sometimes the surgeon will not use a glenoid component. For example, if there is good cartilage still in the glenoid fossa, or conversely, if there is a lot of glenoid deterioration, or badly torn rotator cuff tendons, the surgeon may opt to not use the glenoid implant component (see Stemmed Hemiarthroplasty).
For the humerus part of the implant the upper portion of the bone is hollowed out; this is similar to the process that is done in hip replacement surgery. A metal implant is then inserted into the hollowed out humerus. The metal stem of the implant may be secured with bone cement. A portion of the implant sticks out of the humerus bone where the head used to be; this is where a new metal head, or ball, is attached. Both parts are now present: the ball and the socket. The surgeon then places the ball (head of the humerus implant), into the socket (glenoid fossa component), and makes sure that it is secure and stable, yet still has good mobility. Different sized components are used to make sure the fit is just right for your body. After the joint is repaired, the incision is then sutured or stapled closed.
Following surgery, you will be given antibiotics and pain medications. You will also be required to wear an arm sling for support, and to protect the joint from excessive movement while it is healing. The sling is typically worn for 3-4 weeks or up to 6 weeks. A physical therapy regimen will be prescribed to help you gradually regain strength, stability, and range of motion. Sometimes you will be allowed to use your arm for some simple activities as soon as the next day.
Stemmed Hemiarthroplasty
This is another option for shoulder replacement surgery candidates. If the condition of the joint warrants it, your surgeon may only replace the ball (humeral head) of the shoulder joint. This procedure is similar to the total shoulder replacement surgery, however, there is no glenoid component used during the procedure. This is called a stemmed hemiarthroplasty, because only the head of the humerus is replaced with a metal ball and stem component. This option is recommended when the socket (glenoid fossa) has healthy and intact cartilage, or conversely, if there is just too much damage to the rotator cuff tendons, or poor quality bone in the glenoid fossa. Note that sometimes the surgeon has to make the decision for a hemiarthroplasty or a total shoulder replacement while in the operating room.
The “Ream and Run” arthroplasty is a variation of the stemmed hemiarthroplasty. This procedure is the same as the stemmed hemiarthroplasty. Additionally, a special tool called a reamer is used to shape the glenoid fossa into a more cup-like shape. This gives the joint more surface area, and can promote the growth of fibrocartilage on the surface of the glenoid fossa. This fibrocartilage acts to protect the joint surface from wear and tear. This procedure can be a good option for younger patients, those patients with healthy bone, and those patients who are able to adhere to the rigorous daily exercise program. This procedure can restore high levels of comfort and function to certain patient populations.
Following surgery, you will be given antibiotics and pain medications. Like the total shoulder joint replacement you will be required to wear an arm sling for support, and to protect the joint from excessive movement while it is healing. The sling is typically worn for 3-4 weeks or up to 6 weeks. A physical therapy regimen will be prescribed to help you gradually regain strength, stability, and range of motion. Sometimes you will be allowed to use your arm for some simple activities as soon as the next day.
Reverse Total Shoulder Replacement
This is another option for total shoulder joint replacement surgery. This option is typically used for patients who have completely torn rotator cuff tendons with associated weakness in the arm. It is also used for patients who have severe arthritis plus rotator cuff tearing, and it is used for patients who have had a previous shoulder replacement procedure that has failed. The term reverse in the name reverse total shoulder replacement refers to the swapping of the ball and the glenoid components locations. In the standard shoulder replacement surgery, the head of the humerus is replaced with a new, metal head, and the glenoid fossa is replaced with a new, plastic glenoid fossa component. In the reverse total shoulder surgery, the metal ball component (head) is attached to the glenoid fossa area, and the plastic socket (glenoid component) is attached to the humerus bone. This switching out of the components allows different muscles (deltoid muscles) of the shoulder to initiate lifting of the arm. In normal shoulder functioning, the muscles of the rotator cuff aid in lifting of the arm. However, in those patients who have badly torn and damaged rotator cuffs, this cannot occur. Thus, the reverse total shoulder replacement procedure was developed to change the dynamics of how the shoulder and arm work together. The deltoid muscles can now be used to provide the movement in the shoulder joint.
Like the standard total shoulder joint replacement, the humeral component has a stem which is inserted into the bone, and then a plastic cup-shaped piece is placed on top of it. The glenoid fossa will have a metal ball component attached to its surface. However, before the final components are implanted, the surgeon will use trial implants to determine the correct size, angle, and fit of the implants for your particular anatomical needs. Once the correctly sized implants are determined, the final components can then be attached. After the joint stability, tension, and range of motion are assessed, the surgery can be completed. The incision is then sutured or stapled closed.
Following surgery, you will be given antibiotics and pain medications. You will also be required to wear an arm sling for support, and to protect the joint from excessive movement while it is healing. The sling is typically worn for 3-4 weeks or up to 6 weeks. A physical therapy regimen will be prescribed to help you gradually regain strength, stability, and range of motion. Sometimes you will be allowed to use your arm for some simple activities as soon as the next day.
Resurfacing Hemiarthroplasty
This procedure involves replacing just the joint surface of the humeral head with a metal cap. This procedure has the advantage of preserving more of the bone of the humerus, as there is no need to deeply drill out the humerus to fit the longer stem of the standard stemmed shoulder replacement. This procedure, much like the Stemmed Hemiarthroplasty, may be an option if there is still intact cartilage on the glenoid fossa, if there is no fracture of the head or neck of the humerus, and if there is a desire to preserve maximal humeral bone. The resurfacing hemiarthroplasy may be converted to a total shoulder replacement if necessary in the future.
Following surgery, you will be given antibiotics and pain medications. You will be required to wear an arm sling for support, and to protect the joint from excessive movement while it is healing. The sling is typically worn for 3-4 weeks or up to 6 weeks. A physical therapy regimen will be prescribed to help you gradually regain strength, stability, and range of motion. Sometimes you will be allowed to use your arm for some simple activities as soon as the next day.
This page is for information purposes only, and describes general information. You should always talk to your physician regarding specific details of your surgery.
References
https://orthoinfo.aaos.org/en/treatment/articular-cartilage-restoration/
https://orthoinfo.aaos.org/en/treatment/shoulder-joint-replacement/
Matsen, FA, Int. Orthop. 2015 Feb;39(2):255-61. doi: 10.1007/s00264-014-2641-2. Epub 2015 Jan 24.
Aldinger PR, Int Orthop. 2010 Apr; 34(4): 517–524. doi: 10.1007/s00264-009-0780-7. Published online 2009 Apr 28.
This page is for information purposes only, and describes general information. You should always talk to your physician regarding specific details of your surgery.