Two Approaches to Osseointegration Surgery

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By Fred Hernandez

Osseointegration is rapidly expanding in North America, yet there remains confusion over implant design, rehabilitation protocols, and cost. There are two osseointegration (OI) systems most commonly being used in the United States today: the original screw-fixation system, the Osseoanchored Prostheses for the Rehabilitation of Amputees (OPRA) Implant System, manufactured by Integrum AB in Mölndal, Sweden, and press-fit implants that are manufactured by various companies. In the United States, OPRA is only available for people with transfemoral amputations and is performed via a two-stage technique with six months between the first and second stage.

Jason Stoneback, MD, director of the Limb Restoration Program at the University of Colorado (UC) School of Medicine and UC Health says that to his knowledge he is the only surgeon in North America using both the screw fixation and press-fit techniques.

"I feel it's important to be well-versed in both techniques to allow the patient to have an unbiased opinion of the pros and cons of each technique and allow us to choose the best option for the patient, patient's anatomy, and their overall treatment goals," he says.

 

Methods

The OPRA, or screw-fixation technique, was developed from dental implant osseointegration and uses a hollow screw fixture buried in the bone that develops a structural and functional connection between the bone and the artificial implant. Connection of an abutment to the implant is made during the second stage of the procedure and protrudes through the skin to provide the attachment for the prosthesis. The procedure does not provide immediate stability and requires six months for full osseointegration.

The press-fit technique uses technology common in orthopedic joint replacement surgery. "The implants have a solid core and are porous-coated, and then press fit into the amputee's residual limb. Unlike the OPRA screw-fixation technique, the press-fit technique allows immediate implant stability, just like a hip replacement, allowing earlier weight bearing," Stoneback says.

 

Stoma

From a surgical perspective, Stoneback says that the stoma, where the pin protrudes through the skin, is very different depending on the implant technique being utilized. With the OPRA technique, the stoma is created during the second-stage surgical procedure by soft-tissue rearrangement.

"Creation of a muscle platform gives the residual limb its characteristic square shape followed by skin grafting the stoma skin onto the distal end of the bone," he says. "Once healed, the stoma is tethered to the distal end of the bone and moves with the bone as a unit.

"With the press-fit technique, the stoma is created by having the major soft-tissue rearrangement performed during the first surgical stage. Excess soft tissue and muscle is removed during the first stage of the procedure followed by creation of the actual stoma during a minor outpatient second-stage surgical procedure," Stoneback says. "Once the stoma has healed after the second-stage procedure it is typically slightly mobile but may be adhered to the bone and soft tissues beneath."

 

Rehabilitation

Rehabilitation also differs between the surgeries. Stoneback says that between the first and second procedures of the screw-fixation procedure, the patient is allowed to use a prosthetic socket, but it rarely occurs. Rehabilitation includes a two- to three-day hospital stay after the first procedure, and a stay of about one week following the second procedure. "During the second-stage procedure there is more soft-tissue rearrangement and…skin grafting the stoma to the distal end of the femur, which requires restrictions on mobility to allow the skin to heal to the bone."

For six weeks following the second procedure, the patient is non-weight bearing with limited hip range of motion.

"After the six-week, non-weight bearing period, the patient then begins weight-limited axial loading on a bathroom scale with a short pilon for four weeks followed by four weeks of axial loading on a bathroom scale with a long pilon, and then they transition to their prosthesis to begin gait training," Stoneback says. "The goal is to be weight bearing unassisted at one year from the first-stage surgical procedure."

Press-fit rehabilitation allows for earlier weight bearing than with OPRA fixation implants. While the process varies, Stoneback's protocol consists of the first-stage surgical procedure, with a two- to three-day hospital stay after which the patient is non-weight bearing on his or her residual limb, and unlike the OPRA procedure, the patient cannot use a prosthetic socket. Six weeks later, an outpatient second-stage procedure is performed, followed by prosthetic fitting and weight bearing about two days later. "The goal is progressive weight bearing after the second-stage surgical procedure with the goal of walking with limited assistive devices approximately three months after the first-stage procedure," Stoneback says.

While press fit can be done in a single-stage or a dual-stage procedure, Stoneback recommends the two-stage technique for people with transfemoral amputations. "Due to the larger and more robust soft-tissue envelope, [the dual-stage procedure] has the longest and most successful reported track record in regard to implant retention, lowest infection rates, and lowest rates of post-operative soft tissue complications. The first stage allows the implant to osseointegrate into the bone in a sterile environment and allows the soft tissues to mature prior to the second-stage creation of the stoma. Increased infection rates and over-retraction of the soft tissues during single-stage transfemoral amputations have been noted. Over-retraction of soft tissues can cause exposure of bone and retraction of the soft tissues onto the rough, porous portion of the implant with the single-stage technique."

He says that single-stage press fit may be necessary in transtibial cases because of the soft-tissue envelope, but because there is less muscle and redundant soft tissue in the lower leg, problems are less likely than with single-stage transfem­oral OI.

Stoneback says the Limb Restoration Program has a multidisciplinary team-based approach to care. They treat patients who choose to continue using sockets, sometimes through lengthening of short residual limbs, patients interested in osseointegration, or those who are having problems with their existing OI, including infection and soft tissue- or stoma-related problems.

As there can be a significant cost difference between the two systems, even with insurance companies covering the procedure, costs should be considered when researching the best system in individual situations. External components will need to be replaced as their warranty expires, so maintenance expenses may also be a factor in the choice of screw-type or press-fit osseointegration decisions.

 

Fred Hernandez, president of AmpUtek, Las Vegas, manages a medical device distribution company that specializes in OI implants and related components. He began working independently in the field in 2012.